Front Cover
 Table of Contents

Group Title: Bulletin
Title: The Black scale
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00095573/00001
 Material Information
Title: The Black scale
Physical Description: 3, p. 151-200 : ill., maps ; 23 cm.
Language: English
Creator: Quayle, H. J. ( Henry Josef ), 1876-
Rust, E. W. ( Everett Winder ), 1884-
Donor: unknown ( endowment )
Publisher: Agricultural Experiment Station, University of California
Place of Publication: Berkeley, Cal.
Publication Date: 1911
Subject: Scale insects   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by H.J. Quayle ; assisted by E.W. Rust.
Bibliography: Includes bibliographical references (p. 199-200).
General Note: Cover title.
General Note: At head of title: University of California publications. College of Agriculture. Agricultural Experiment Station, Berkeley, California.
General Note: University of California Agricultural Experiment Station bulletin 223
 Record Information
Bibliographic ID: UF00095573
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 14050594
lccn - a 34001015

Table of Contents
    Front Cover
        Page 147
        Page 148
    Table of Contents
        Page 149
        Page 150
        Page 151
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        Plate 1
        Plate 2
        Plate 3
        Plate 4
        Plate 5
        Plate 6
        Plate 7
        Plate 8
        Page 195
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Full Text










BENJAMIN IDE WHEELER, President of the University.


E. J. WICKSON, M.A., Director and Horticulturist.
E. W. HILGARD, Ph.D., LL.D., Chemist (Emeritus).
W. A. SETCHELL, Ph.D., Botanist.
LEROY ANDERSON, Ph.D., Dairy Industry and Superintendent University Farm Schools.
M. E. JAFFA, M.S., Nutrition Expert.
R. H. LOUGHRIDGE, Ph.)., Soil Chemist and Physicist (Emeritus).
C. W. WOODWORTH, M.S., Entomologist.
RALPH E. SMITH, B.S., Plant Pathologist and Superintendent of Southern California
Pathological Laboratory and Experiment Station.
G. W. SHAW, M.A., Ph.D., Experimental Agronomist and Agricultural Technologist, in
charge of Cereal Stations.
E. W. MAJOR, B.Agr., Animal Industry.
B. A. ETCHEVERRY, B.S., Irrigation Expert.
F. T. BIOLETTI, B.S., Viticulturist.
W. T. CLARKE, B.S., Assistant Horticulturist and Superintendent of University Exten-
sion in Agriculture.
JOHN S. BURD, B.S., Chemist, in charge of Fertilizer Control.
J. E. COIT, Ph.D., Assistant Pomologist, Plant Disease Laboratory, Whittier.
GEORGE E. COLBY, M.S., Chemist (Fruits, Waters, and Insecticides), in charge of
Chemical Laboratory.
H. J. QUAYLE, M.S., Assistant Entomologist, Plant Disease Laboratory, Whittier.
H. M. HALL, Ph.D., Assistant Botanist.
C. M. HARING, D.V.M., Assistant Veterinarian and Bacteriologist.
E. B. BABCOCK, B.S., Assistant Agricultural Education.
W. B. HERMS, M.A., Assistant Entomologist.
J. H. NORTON, M.S., Assistant Chemist, in charge of Citrus Experiment Station, River-
W. T. HORNE, B.S., Assistant Plant Pathologist.
C. B. LIPMAN, Ph.D., Soil Chemist and Bacteriologist.
R. E. MANSELL, Assistant Horticulturist, in charge of Central Station grounds.
A. J. GAUMNITZ, Assistant Agronomist, University Farm, Davis.
N. D. INGHAM, B.S., Assistant in Sylviculture, Santa Monica.
T. F. HUNT, B.S., Assistant Plant Pathologist.
P. L. MCCREARY, B.S., Chemist in Fertilizer Control.
E. H. HAGEMANN, Assistant in Dairying, Davis.
R. M. ROBERTS, Farm Manager, University Farm, Davis.
B. S. BROWN, B.S.A., Assistant Horticulturist, University Farm, Davis.
J. I. THOMPSON, B.S., Assistant Animal Industry, Davis.
HOWARD PHILLIPS, B.S., Assistant Animal Industry, Davis.
J. C. BRIDWELL, B.S., Assistant Entomologist.
C. H. MCCHARLES, M.S., Assistant Agricultural Chemical Laboratory.
E. H. SMITH, M.S., Assistant Plant Pathologist.
C. O. SMITH, M.S., Assistant Plant Pathologist, Plant Disease Laboratory, Whittier.
F. E. JOHNSON, B.L., M.S., Assistant Soil Chemist.
B. A. MADSON, B.S.A., Assistant Experimental Agronomist.
WALTER E. PACKARD, M.S., Field Assistant Imperial Valley Investigation, El Centro.
P. L. HIBBARD, B.S., Assistant Fertilizer Control Laboratory.
L. M. DAVIS, B.S., Assistant in Dairy Husbandry, University Farm, Davis.
S. S. ROGERS, B.S., Assistant Plant Pathologist, Plant Disease Laboratory, Whittier.
L. BONNET, Assistant Viticulturist.
H. A. RUEHE, B.S.A., Assistant in Dairy Husbandry, University Farm, Davis.
F. C. H. FLOSSFEDER, Assistant in Viticulture, University Farm, Davis.
S. D. WILKINS, Assistant in Poultry Husbandry, University Farm, Davis.
C. L. ROADHOUSE, D.V.M., Assistant in Veterinary Science.
F. M. HAYES, D.V.M., Assistant Veterinarian.
F. L. YEAW, B.S., Assistant Plant Pathologist, University Farm, Davis.
M. E. STOVER, B.S., Assistant in Agricultural Chemical Laboratory.
W. H. VOLCK, Field Assistant in Entomology, Watsonville.
E. L. MORRIS, Field Assistant in Entomology, San Jose.
E. E. THOMAS, B.S., Assistant Chemist, Plant Disease Laboratory, Whittier.
A. B. SHAW, B.S., Assistant in Entomology.
G. P. GRAY, M.S., Chemist in Insecticides.
H-. D. YOUNG, B.S., Assistant in Agricultural Chemistry, Plant Disease Laboratory,
A. R. TYLOR, B.S., Assistant in Plant Pathology, Plant Disease Laboratory, Whittier.
E. W. RUST, A. B., Assistant in Entomology, Plant Disease Laboratory, Whittier.
L. T. SHARP, B.S., Assistant in Soils.
W. W. CRUESS, B.S., Assistant in Zymology.
J. F. MITCHELL, D.V.M., Assistant in Veterinary Laboratory.
J. C. ROPER, Patron, University Forestry Station, Chico.
E. C. MILLER, Foreman, Forestry Station, Chico.
D. L. BUNNELL, Secretary to Director.


HISTORICAL --------------------------------- 151
DISTRIBUTION -------------------------------------- -- 151
ECONOMIC IMPORTANCE ------------------- ------------- 153
NATURE OF INJUBY---------------------------------- ------- 154
FOOD PLANTS -------------- --------------------- 155
THE EGG ----------- 157
Description -------------- 157
Incubation period --------------- 157
Number -------------------------------- 157
Percentage that hatch --------- -------------------- 157
Season when most abundant -------- ----------------- 157
Relation of weight of eggs to weight of body ----- --------------158
Hatching records --------------------------------------159
THE ACTIVE LARVA __. -------- --_-------- --_---.--- 160
Description ---------------------------------------- ------ 160
Emergence ---------- --------160
Locomotion --- ------------------ 161
Rate of travel over smooth surfaces ----------------------------- 163
Rate of travel over sand and orchard soil---- ------------------_ 163
Other factors in the spread of the young scale -- ---------------- 164
Length of life without food ----------------------------------- 165
Experiments on the effect of temperature--- ------------------ 165
Effects of light-------------------------------- 166
Where the young settle--------- --------------------- 167
Proportion of young becoming fixed ---- ------------- 168
THE FIXED YOUNG -------------------------------- 168
Development before first molt------------------------------------- 168
The first molt------------------------------------ 169
Development between first and second molts -------- ------------- 169
The second molt of the female------------------------_________ 169
Process of molting---------------------------------------------- 169
Effects of temperature------------------------- ------------- 169
Honeydew and fungus growth------------------ ------------ 170
Relation of ants to the scale --------------------------- 170
Movement after settling------------------ ----------------------- 170
THE ADULT FEMALE--------------------------- 172
Description ------------------------------------------------ 172
Oviposition ------------------------------------------ --- 172
THE DEVELOPMENT OF THE MALE------- --------------- -------- 173
The second stage male--------------------------- 173
The male puparium---------------------------- ----------- 173
The propupa ------------------------ 175
The pupa ---------------------------------------- ----- 175
The adult male------------------------------------ ------- 175
SEASONAL HISTORY -- ---- ---------------- 176
Number of generations ------- ----------- __ ---- 176
Mortality at different seasons---------------------------------- 177
Annual progeny of a single scale ------------------------- ___--- 178

PARASITES -------------------------------------- 179
SCUTELLISTA CYANEA Motsch.._____---------------_--_ 179
History of introduction . . . --. ------- 179
Economic importance and present status in California -- 180
Distribution -- -- --------- -- ------ 181
Description-Life history--Habits -------------- 181
The egg-Description--Where found-Length of stage -------- 181
THE LARVA ---------------- 182
Description, amount of food, length of larval life-- _---- 182
TIIE PUPA ---------------------------183
Description, length of stage_--------- ______ 183
THE ADULT --------------------------- -- 184
Description -- ---------------------- 184
Oviposition __------------- -- _- 184
Proportion of the sexes -- ____------__ 185
Pathenogenesis ------------------85
Length of adult life -------------- 186
SEASONAL HISTORY -------------180
NUMBER OF GENERATIONS ------ __ ----- 180
IYPERPARASITE. Cerchysius sp.- ---------- 187
The larva -------------------------------- 187
The adult-------------------------------- 187
TOMOCERA CALIFORNICA HOW --------------- --------- 189
Description and life history------------ 189
APrIYCUS FLAVUS HOW.------------------------------------ 190
The larva, pupa and adult------------ 190
PREDACEOUS ENEMIES_ ------------ 192
RHIZOBIUS VENTRALIS ------ ------------------- 192
BLACK SCALE ---------------------------------------- ----- 194
SAISSETIA HEMISPIIAERICA ------------------------------------ 194
COCCUS HESPERIDUM -------------------------------------- 194
LECANIUM CORNI ------ ----------------- ------------- 19
LECANIUM PRUINOSUL --------------------------------------- 190
LECANIUM sp. ---_ -------------------------------- 196
SYSTEMATIC POSITION ------------------------ 19S
BIBLIOGRAPHY ----- -------------------------------- 199


Assisted by E. W. RUST.

The Black Scale, Saissetia olee Bern, is widely distributed over most
of the countries of the world, and has been known as a pest of the olive
in the Old World nearly as far back as our entomological records go.
It was first described by a Frenchman named Bernard* from specimens
taken on olive in 1782. It was given the specific name olece from the
host plant on which it was originally found. Articles have since
appeared on this insect in various countries, so that the list now totals
more than 100 papers.
Just when it was introduced into California, or from what country,
doesn't appear to be established. The first complete account of its
occurrence here is given in Comstoc'k's report for 1880. It had been in
the State, however, many years previous to that time. By 1880 it was
well established in various parts of the State, and found infesting a
wide range of food plants; but it was at that time, as now, a particularly
serious enemy to citrus trees. It was given the common name of "Black
Scale of California." Since this was the first reference to this scale in
the literature of this country, and because of the common name applied,
it appears that it was unknown in the United States, at that time, out-
side of California.

The following localities give the present distribution of S. oleos over
the world: Aldabia, Mauritius, Europe, New Zealand, Australia, China,
Japan, Java, Africa, Ceylon, Brazil, W. Indies, Mexico, France, Italy,
Spain, Massachusetts, South Carolina, Ohio, Florida, and California.
In California it occurs to a greater or less extent in practically all of
the counties. As a pest it is limited to the citrus belt of southern Cali-
fornia, the different deciduous trees in the coast counties about San
Francisco Bay, and to some extent on olive trees of the interior valleys.
It occurs throughout the valleys on oleander and olive in varying
degrees, but is not often serious enough to warrant treatment. In cer-
tain places in the lower Sacramento Valley it has become abundant
enough on the olive to necessitate spraying.
In the citrus area of southern California, the black scale is the most

*1 Mem. d'Hist. Nat. Acad., Marseilles, p. 108 (1782).

FIG. 1.-Map showing distribution of the Black Scale over the world.


widely distributed of all the scale pests. It occurs in all of the counties
from Santa Barbara to San Diego. It is less abundant in the interior
counties of Riverside and San Bernardino; but even here in some sec-

SANTA ---.-------- S AN

,' LOSAnqeleiS% ^ ,' ** -



FIG. 2.-Distribution of Black Scale in Southern California.

tions it becomes an important pest. But the black scale becomes most
abundant nearer the coast since it is a scale that is more adapted to the
cooler and moister climate of such sections.

The black scale is probably entitled to first rank as a citrus fruit pest
in southern California. It has this place in Los Angeles, Orange, and
Santa Barbara counties. This is based upon a report* of the respective
horticultural commissioners of those counties. In two other counties,
San Diego and Ventura, it has second place as a pest. First place in
San Diego County is pre-empted by the purple, but because of the wider
distribution of the black, it might be considered as the more important
of the two. In Ventura County while the citrus mealy bug is put first,
the commissioner states that practically all the control work is directed
against the black. This is the real test of the economic importance of
an insect, so that the black scale should be given first place in that
county. In Riverside and San Bernardino counties the black ranks
third as a pest. In these counties the yellow is given second place, but
*Bulletin 214, Cal. Ex. Sta., p. 446, 1911.



if we consider the red (Chysomphalus aurantii Mask) and the yellow
(Chrysomphalus aurantii var. citrinus Coq.) as one species then the
black will occupy second place in these two counties. It will be noted
also that the Riverside commissioner stated that in 1910 seventy-five per
cent of the control work was directed against the black. This, of course,
is a higher percentage than is usual in that locality for the black scale.
It should be mentioned also that where the purple or red is associated
with the black, the control work is usually aimed at the other species,
because they are more difficult to kill, that is, providing the time is
chosen when the black is in the right stage. But if the black were
allowed to go on untreated it would probably do as much as or more
injury than the others.
Nature of Injury. The chief injury occasioned by the black scale is
not due so much to the loss of sap through feeding, nor to the toxic
effect on the tissues, as seems to be the case with the armored scales.
That more or less injury of the above nature is done is not questioned,
for it must be this largely that causes an actual killing of twigs where
the scales are incrusted
upon them. But so far as
7 citrus fruits are concerned,
S' the important injury is due
S. .- to the sooty mold fungus
-' Meliola camellia (Catt)
' Sace., which grows in the
^ 'excretion, or so called
A honeydew. Large quanti-
Ui. L ties of this honeydew are
excreted, which falls upon
the upper surfaces of the
j leaves and fruit, and serves
b as a medium for the growth
of the fungus. This com-
plete coating, as is often
FIm. 3.-The sooty mold fungus. Much enlarged. i
1. Mycelium. 2. Conidia. 3. Pycnidia with im- found on the leaf, inter-
mature spores. From Florida Bulletin No. 53. feres with the naturalfunc-
tions of the leaf by shutting off light. Light is necessary for the forma-
tion of starch and sugar, and consequently the sugar content of the
fruit may be greatly reduced. The interference with the normal func-
tions of the leaves also tends to diminish the general vigor of the tree.
But the great injury due to this scale is simply the presence of the
sooty mold fungus on the fruit. For oranges or lemons to appear
attractive and sell, they must be bright and clean. The proper way to
get such fruit is to keep the tree free from the causative agent, in this


case the black scale. But where the treatment is not properly done, or
not done at all, the next best way to secure clean fruit is by washing.
This operation in itself adds to the cost of handling, but the most im-
portant injury here is in rendering the fruit more likely to decay. With
the fruit coming in contact with the sides of the tank, brushes, elevators,
and drying racks, it is impossible to escape some abrasions, and into
these abrasions the spores of the following fungi, with which the wash
water may be infected, may find their way: Blue Mold, Penicillium
italicum Wehmer; green mold, Penicillium digatum Sacc.; brown rot,
Phythiacystis citrophthora Smith; cottony rot, Sclerotinium; Botrytis
cinera Pers. and Aspergillus niger Van Tiegh.

While the total list of food plants of the black scale is a long one, the
number that is seriously infested is not large. In California it ranks
first as a pest on citrus trees. On the olive, pepper and oleander, it also
occurs in abundance, and often does much injury, but it is only rarely
that control work is undertaken on these trees. Of the deciduous trees
the apricot and prune are the worst attacked. On these trees Lecanium
corni is often associated with the black, and is the more important pest
of the two in the deciduous fruit sections. But the black scale often
does reach the status of a pest on these trees and spraying is done to
control it. It is not uncommon to see apricot trees completely covered
with sooty mold fungus as a result of black scale infestation.
The plants named practically conclude the list on which the black
scale is really an economic pest in this State. Many others are attacked,
but are of interest chiefly in that they serve to reinfest those commercial
trees that may be growing about them. It is not uncommon to find a
citrus grove with the borders and avenues lined with peppers or olives.
These serve as an excellent breeding ground, for they remain untreated.
On the other hand, these trees are believed to be a distinct benefit
because they insure the perpetuation of Scutellista, in the interim that
the scale in the grove itself is recovering from the effects of fumigation.
But if the grove is regularly fumigated, and the Scutellista thus ignored,
such a claim is illogical. If the Scutellista, by being maintained on the
peppers, tend to prolong the time for the next fumigation then they are
a distinct benefit. Anyway, such shade trees as the pepper seem to be
necessary for the comfort and esthetic value they afford, and since it is
impossible to prevent reinfestation with such an insect as the black
scale anyway, to cut down such trees, as is sometimes advocated, hardly
seems justifiable.



The list of food plants from which the black scale has been taken is as
follows: Orange, lemon, guava, irish juniper, lombardy poplar, apricot,
prune, plum, almond, sycamore, oleander, pepper, Rhus, Heteromeles,
Baccharis, Ficus, Habrothamnus, Myosporum, Melaleuca, laurel, holly,

I -A t1
FIG. 4.-Black Scale (Saissetia oleae Bern.)
on orange twig.

beech, ash, Rhamnus, Acer, Grevillea, Ligustrum, night shade, Anti-
desma, Duranta, Grewia, Thespesia, Cajanus, apple, pear, olive, pome-
granate, Oregon Ash, honey locust, Magnolia, Eucalyptus, coffee, rose,
Vitis, Camellia, Terminalia.


Description. The eggs are oval in shape, measuring .3 mm. long and
.2 mm. wide. When first deposited they are usually pearly white, but
soon change to a cream color or with a pinkish cast. As the develop-
ment continues they pass through different shades of pink until a few
days before hatching they assume a reddish orange hue. The eye spots
now appear and the embryo may be made out within.
Incubation Period. Several hundred freshly deposited eggs were
placed in a pill box in the laboratory on June 9th. On June 24th a
few hatched, about four fifths of the number hatched on the 28th, while
the last hatched on the 29th. The minimum incubation period under
these conditions was 16 days and the maximum 20 days. Other lots
of eggs laid on June 16th hatched in from 19 to 21 days. During the
winter season hatching may be prolonged for a month or six weeks.
Number of Eggs. Counts made of the number of eggs from 10 differ-
ent scales of various sizes were as follows: 319, 220, 2073, 839, 2058,
2536, 1340, 1542, 2894, 2823. The number will thus vary from about
200 to 2900, the average in averaged sized scales will run close to 2000
Percentage of Eggs that Hatch. In nearly all cases practically all of
the eggs hatch. It is only very rarely that eggs will be found beneath
the scale and not hatched. But it is rather common to find a large num-
ber of young dead beneath the parent. This is probably due to their
inability to emerge on account of the arch at the posterior tip being in
close contact with the twig or through the clogging of the opening by old
egg skins or young that have died from some other cause. It is possible
also that extreme heat may kill the young before they emerge. Heat is
an important factor in their mortality after they emerge.
Season when Eggs are Most Abundant. The eggs of the black scale
may be found in certain localities at any season of the year. But by
far the largest number of eggs occur in the spring during May, June,
and a portion of July. At this season the great majority of the scales
will be found with eggs in any part of the citrus area, but at other times
there may be no eggs in certain groves, while in others eggs will be
found. In this connection the time of fumigation may have an impor-
tant influence on the stage of the insect, since all the young and partly
grown may be killed, while the eggs under the adults will escape the
effects of the gas. But there is, aside from this, a natural off hatch
which occurs whether the tree has been fumigated or not. During the
season of 1910 the largest number of eggs were present in the latter
part of May.



Relation of Weight of Eggs to Weight of Body. The following table
gives the weight of the scale with and without eggs, the difference being
the weight of the eggs alone. It will be seen that the eggs comprise a
trifle less than one half of the body weight.
1 2 3 4 5
Weight of scale and eggs--- .014 grams .018 .012 .019 .012
Weight of scale-------------------- .008 .08 .006 .009 .006
Weight of eggs ------ .006 .010 .006 .010 .006
6 7 8 9 10
Weight of scale and eggs------------ .020 grams .009 .017 .008 .007
Weight of scale --------- .009 .005 .008 .005 .004
Weight of eggs ------ .011 .004 .009 .003 .003
The 10 scales indicated in the above table were picked from the twigs
with their full quota of eggs at that time. This was when the eggs
were present in their maximum numbers. All of the eggs, of course,
are not present at any one time, since the period of oviposition is greater
than the hatching period. Consequently, more eggs would be deposited
later so that instead of the weight of eggs being slightly less than that
of the body as indicated in the table the total number laid will exceed
one half the body weight.
Hatching Records. The scales represented in the following table
were slightly under medium size. They were infesting oleander leaves
and each one was surrounded by a ring of tree tanglefoot so that the
young were imprisoned as they emerged. Each day they were counted
and removed. The records of the 13th, 20th and 27th each represent
a two days' hatch. It will be noted that the hatch roughly follows the
temperature changes. During the cooler weather the young seem to
remain under the scale longer and emerge in larger numbers on the next
warm days.


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Description. Length .34 mm., width .2 mm. The color is light
brown; eyes black, antennae 6 segmented. From each of the oval plates
there arises a long spine, slightly more than half the length of the body.
The body is very flat and oval in shape.
Emergence. In all cases observed the young larve make their way
from beneath the parent under the arch at the posterior tip. This arch
consists of a slightly raised portion of the scale, for a short distance on
either side of the anal cleft, which is not attached to the twig. This is
large enough to permit of the exit of the young scales and occasionally
two have been seen emerging side by side. The emergence occurs at
about the same rate as the hatch, although many young will be seen
under a scale at one time. But since about 40 eggs are laid in a day,
this number may hatch at the same time, and these, together with the
early or late hatching of others deposited near the same time, accounts
for the large number that occur under the scale. They may remain
under the scale for a day or two, so that when they emerge they have
their full strength and begin immediately to actively crawl about.
Locomotion of the Young Larvce. The distance traveled by the active
larva on smooth paper was an average of 71 inches during a two-hour
period when the temperature was 73.50 F. The higher the temperature
the faster they would travel, so that with a temperature of 90 F. they
traveled in the same time a distance of 151 inches.


FIG. 5.-Tracings of young black scales for a 2-hour period. Reduced 7 times.
Temperature 73.5 degrees. Average distance 71 inches.

FIG. 6.-Tracings of young black scales for a 2-hour period. Reduced 7 times.
Temperature 80 degrees. Average distance 76 inches.


- '.--.. C-- -
9- N



FIG. 7.-Tracings of young black scales for a 2-hour period. Reduced 7 times.
Temperature 83 degrees. Average distance 123 inches.

i /,, . ,9 : ,,' .... .
/ .o-.--,.. ... ..-- ---- -----

- /

FIG. 8.-Tracings of young black scales for a 2-hour period. Reduced 7 times.
Temperature 90 degrees. Average distance 151 inches.

- -


Table Showing Rate of Travel Over Smiooth Surface.
Tempera- Avemage
x. No. Date. Time..- Distance. dance.

1 November 2, 1910 -------------- 1:45- 3:45 73.5 70 inches
1 November 2, 1910 ----- -. 1:45- 3:45 73.5 62 inches
1 November 2, 1910 .. -- 1:45- 3:45 73.5 81 inches 71 inches
2 July 5, 1910 -------- 2:15- 4:15 80 73 inches
2 July 5, 1910 -- 2:15- 4:15 s80 80 inches 76 inches
3 August 17, 1910 ----- 9:30-11:30 83" 103 inches
3 August 17, 1910--- --- 9:30-11:30 83 140 inches
3 August 17, 1910----- 9:30-11:30 83* 127 inches 123 inches
4 July 19, 1910 -----.. --- 2:10- 4:15 00' 108 inches
4 July 19, 1910. ------- 2:15- 4:15 90D 166 inches
4 July 19, 1910- --- - 2:15- 4:15 90 180 inches 151 Inches

May 31, 1910. Temperature 840 at point of experiment. 3: 30 p. m.
Several dozen young (taken from under adult) were placed upon leveled
sand in a dish. At 3: 55 one reached the edge of the dish, at 4: 02 two
more, and 5 more at 4: 30. At 5 p. m. dozens had reached the edge of
the plate. The distance traveled was 4 inches.
June 1, 1910. 10:20 a. m. Temperature 780 at point of experi-
ment. Several active young were liberated in the center of a plate of
average lumpy orchard soil. In one hour 10 reached the edge; at noon
about 50 more, and by 1 p. m. nearly all the young scale had reached
the edge of the plate. Distance traveled, 4 inches.
June 1, 1910. 9:15 a. m. Temperature 740 to 840. Several hun-
dred young were placed on a board covered with fine dust. By 1 p. m.
nearly all had died, possibly from the suffocating effect of the fine
particles of dust. The most active had traveled but 28 inches. Insects
used as a check showed no ill effects under the same conditions except-
ing that they were on clean paper.
June 1, 1910. 10:10 a. m. Temperature 800 at surface of sand.
Several hundred young were liberated in the center of a dish containing
sand with the surface smoothed over. This dish was then placed under
a cover which allowed the light to strike strongly on one side. By
10: 50 a. m. the majority of the insects had reached the lighted side of
the box, having traveled 5 inches in 40 minutes. At 11: 30 the dish
was revolved 1800 and the insects again thrown in the shadow. By
1 p. m. they had crossed the plate, a distance of 10 inches in 11 hours.
At 1: 30 p. m. the dish was again revolved and the insects again crossed
the 10 inches in 14 hours.
June 3, 1910. 10:15 a. m. Temperature 850. A plot of average
orchard soil was enclosed within strips of paper each 2 feet long. In
the center of this area of soil 400 or 500 active young were liberated.
By 12: 30 p. m. about 20 insects reached the edge; by 1 p. m. nearly 50
and at 5 p. m. about 100. Distance traveled, 1 foot.
2-BUL. 223


June 3, 1910. 10:15 a. m. Temperature 850. A plot of orchard
soil one foot square was enclosed in paper and in the center of this
several hundred young were placed. At the beginning of the experi-
ment the morning was foggy. At 11:05 three insects reached the
paper, a distance of six inches. By this time the sun was appearing
and the temperature rose to 960. Later 102' was reached and all the
insects died.
June 9, 1910. 10:00 a. m. Temperature 73. A plot of ordinary
orchard soil two feet square was enclosed with strips of paper. Several
thousand scales just removed from beneath adults were liberated. At
11: 30 four reached the paper and at noon 20 more. Temperature at
this time was 76.
The same experiment was repeated on the following day with a tem-
perature of 72' to 860. By 2 p. m. about 75 insects reached the paper.
The same was repeated on the following day, when 8 scales reached the
paper in 1 hour and 5 minutes, and 24 in 3 hours and 50 minutes.
July 18, 1910. Temperature 800, humid. Fifty young were placed
in the center of a plot of sand 6 inches in diameter. In 30 minutes 5
reached the black paper on which the sand was placed, and in three
quarters of an hour one half of the insects had reached the paper.
Distance, 3 inches.
From the above experiments it will be seen that the young black scale
is capable of traveling some distance over ordinary orchard soil, but the
percentage traveling any distance is very small. Much greater progress
is made on a compacted soil than over a fine mulch. It may be pos-
sible for a young black scale to make its way from one tree to another,
but the number that will travel that distance over a mulch is exceed-
ingly small. In the case of soil compacted after a heavy rain or in an
irrigation furrow, it is possible that they would reach even the second
or third tree away. During the time of irrigation they may also be
carried by the flow of the water itself.
Other Factors in the Spread of the Young Scale. A foot bellows was
arranged so as to throw a current of air against a white screen. The
maximum velocity of air from this bellows was stronger than the wind
ever blows in the citrus belt. A branch containing active young scales
was placed in this current, but none were displaced until the branch was
brought to within six inches of the mouth of the bellows. Even then
many withstood the extreme velocity, thus showing that the wind, as it
ordinarily blows, can not be counted a very important factor in dis-
lodging the young black scale. Once the scales were dislodged, they
were carried a short distance as they fell.
Several rags, sticks, pieces of boards, and a pair of gloves were placed


in a tree badly infested with the young black scale. Later, when these
were examined, many young were crawling about over them. It is
altogether likely, therefore, that ladders, gloves, clippers, picking boxes,
and other things used in the harvesting of the fruit are possible means
of infesting a clean grove if these things are immediately or soon used
in the grove. While, then, these things are possible sources of spread,
they are not so important as natural agencies.
About 100 Coccinellids were confined for a day in a jar containing
olive branches badly infested with black scale from which young were
issuing. Upon examination it was found that young scales were being
carried about by the beetles. About one beetle in every 10 or 15 carried
from one to four scales. The slower moving beetles were most likely to
carry the scales. These beetles have also been seen under the natural
conditions of the field to have young scale crawling upon them.
What has thus been actually observed in the case of Coccinellids is
likely to occur also with other insects that frequent scale-infested areas.
Among these, ants may be mentioned, but these are not likely to trans-
port them long distances, for their nests are usually close at hand. The
larvm of Chrysopa and Hemerobius which may feed among the scales
may also be guilty of spreading the scales, and possibly also the adults
of these species. Winged Aphids are also found commonly on orange
trees in the early spring, principally, but these are more apt to be con-
fined to the tender growth which has not yet become infested with
scales. But of all the active insects found on the orange tree the
Coccinellidce are probably the worst offenders in spreading young scale.
Length of Life W',ti ,l- Food. Two or three hundred eggs were
taken from under each of several scales and as the young hatched they
were placed in pill boxes without food. One lot lived about 52 hours;
another 60; a third lot (the majority about 60 hours), while a few lived
for 65 hours; lot 4 lived 56 hours; lot 5 were removed from under the
adults alive; these lived 84 hours; lot 6 were similarly taken from
beneath the parent and they lived 84 hours. Lots 7, 8, 9, 10 were all
taken alive from under the adults and lived 66 hours without food. It
thus appears that between 3 and 4 days is the maximum time that young
black scale will live without food.
Experiments on the Effects of Temperature on the Young. May 31,
1910, 2 p. m. Temperature 1150 F. in sun at surface of ground. Sev-
eral hundred active young (taken from under adult) were liberated on
ordinary orchard soil. At 2:15 when again examined all were dead,
not having moved more than 2 inches.
June 30, 1910, 11 a. m. Temperature 800 in sun 4 feet above soil.
Temperature 1200 with bulb in soil at point of experiment. Several



hundred young liberated on ordinary brown colored soil died within
10 minutes.
June 30, 1910, 11: 05 a. m. Temperature in sun 6 feet above ground
80, slight wind. Temperature at surface of paper 104 to 1100,
sheltered from breeze. Active young removed from parent were lib-
erated on white paper under above conditions and remained active for
2 hours, after which observations were discontinued.
June 30, 1910, 10:25 a. m. Temperature 940 to 1000 at surface of
cardboard. Young scales were placed on this where they crawled about
for 2 hours unharmed by the heat.
July 6, 1910. Liberated a number of young from under adult on
white paper in the sun. Temperature 1060 to 1100. Temperature 4
feet above ground, 98. At 106' they were very lively, but as the tem-
perature increased they moved more slowly and at 110 almost all move-
ment ceased, although a 2 hours' exposure did not kill them.
July 6, 1910, 11 a. m. Temperature 118 at surface of board men-
tioned below. A large number of active young, taken from under
female, were placed upon a brown colored board. Within 5 minutes all
the scales were dead.
July 7, 1910, 11 a. m. Temperature 130' at surface of soil. Tem-
perature 100' four feet above ground in sun. Several young from
under female were placed on ordinary orchard soil under above con-
ditions. Death resulted within 5 minutes. Insects used as a check in
the shade were perfectly normal.
July 8, 1910, 10:30 a. m. Temperature 119' to 1220 at surface of
soil. A large number of young were placed upon common orchard soil
under above conditions. After 15 minutes they were again examined
and found dead, a check lot in the shade remaining normal.
Effects of Light. Several experiments, which will not be detailed
here, were undertaken to determine the behavior of the young black
scales toward light. In all cases they responded to the influence of
light, showing them to be positively phototropic.
In the case of older scales, that is, when they migrate from leaves to
twigs, since they almost invariably become fixed on the under side, it
would appear that they later in life become negatively phototropic.
About 100 active young scales, secured from beneath a female, were
placed upon the middle of an upright stake. Some immediately crawled
downward, but a large majority crawled upward. Upon reaching the
top these did not remain there, but crawled down again, many going
directly to the bottom. A little later they became distributed all over
the stake. Here the effects of the light were not removed so that it can
not be stated whether they have a tendency to go up or down. But


judging from observations in the field there appears to be a tendency to
migrate upward.
Where the Young Settle. The large majority of the young in most
cases select the leaves as a place to settle. They may choose either the
upper or lower surface. If the leaves are exposed to the sun they are
more apt to settle on the lower surface. If, too, the upper surface is
covered with sooty mold fungus, as is often the case, they are more
likely to select the cleaner side of the leaf.
In case the twigs are still tender a considerable number of young
may settle there. They have also been observed to settle on stems that
contained more or less of the corky wood. But the majority upon first
settling select the leaves or tender stems. To be sure, the old scales
are found on very large limbs, but it is only rarely that the active young
settle there. The old are found there usually because of their migration
after they have attained some size on the more tender parts of the tree.
The reason for thus selecting the more tender parts of the tree is
because the tissues are more easily penetrated by the small scales, and
because the liquid parts of the plant are nearer the surface and more
easily obtained. There is a tendency of many scales to settle along the
midrib and along the larger veins. They fix themselves parallel to
the midrib with the central line of the body at the bottom of the ridge,
one half extending up on the midrib and the other half on the leaf
surface. This may be partly for protection since there is a distinct
groove here, but more probably because the sap is more readily obtained
at this point.
On June 12, 1909, 160 active young were liberated on twigs and
leaves, 80 on the twigs and 80 on the leaves. Upon examination on
June 24th, 35 were found established, and these all on the leaves.
On the same date 150 scales were distributed in another place and
on the 24th of June, 57 were found on the leaves, largely along the mid-
rib. On July 30th only a very few remained alive, and an occasional
one was seen on the branch.
On June 10, 1909, 12 young black scales were distributed on each of
the leaves of a terminal twig, excepting the lower two. Fourteen days
later the scales which had settled were distributed as follows: 5 on four
leaves, 7 on two, 13 on one, and 4 and 2 respectively on each of the two
lower leaves on which none were actually liberated. The last examina-
tion, which was made on September 21st, found them still on the leaves.
The end of a lemon branch was isolated with tanglefoot and an
infested olive branch from which young were emerging was entangled
in the twig. Three weeks later many had settled on the leaves and
tender branches, most on the upper side, fewer on the lower side and
least on the tender twigs. Later the majority of those dead were found



on the upper surface. This experiment was carried on in several dif-
ferent places in the Laboratory plot and the results were the same in
each case.
The following table gives the record of those settling in our breeding
experiments in the insectary. Out of 236 liberated 53 or 22.88 per cent
No. No. No. No.
Date. Liberated. Settled. Date. Liberated. Settled.
May 17, 1910---------- 15 1 May 13, 1910---- 6 0
May 17,1910---- 6 1 :May 4,1910--- 6 1
June 0,1910----------- 10 3 Aprill6,1910 ---- 7 2
May 10, 1910 ----- 4 2 May 7,1910---- 15 2
May 10,1910----------- 6 3 May 4,1910---- 5 2
S5 M1910 11 5 May 13, 1910---- 25 1
May 4, 1910------------- 7 4 May 13,1910 25 2
May 4,1910 -------- 5 1 May 17, 1910---- 25 2
May 2,1910---- 7 4 May 17,1910---- 6 2
May 11, 1910-------- 6 2 May 2,1910--- 20 7
May 11, 1910 6 3
May 11,1910------------- 6 3 Total ---- 231; 53
May 13,1910------------- 7 0
22.88 per cent.

Proportion of Young Becoming Fixed. We have shown that in the
case of the red scale about 41 per cent fails to become settled. The
purple is a little more successful in this respect, but the black seems to
be the least successful of the three. In thousands of scales liberated we
have often got a mortality as high as 95 per cent before they became
fixed. In other cases a larger per cent will establish themselves. There
appears, therefore, to be a very wide variation in the per cent that may
settle, but on the whole it is very small. The same facts have been
recorded both from the insectary and the field. Immense numbers of
young scales have been found settled in the field where the number of
adults was not especially large. Again, where the adults are extremely
abundant the young have been found to be very scarce. This statement
is made too with due regard for the presence or absence of the egg
parasite, Scutellista.
Development Before First Molt. Soon after settling the young scales
become flatter and somewhat larger in area. The scale preliminary to
the first molt is just about twice the size of the young after hatching.
The length at this stage is .7 mm. and the width .35 mm., as compared
with .35 mm. in length and .2 mm. in width before settling. The anal
plates instead of being at the extreme tip of the scale, as in the active
larva, are now drawn considerably forward, or rather the posterior mar-
gin of the body has extended backward, and the two lobes inward, so
that the plates are enclosed in a triangular space some distance from the
tip. The long spines are still attached to the anal plates but, on
account of the plates being so far forward, they do not extend as far
beyond the tip of the body. The different relative position of the anal


plates and the character of the anal cleft, it now being practically closed
behind the plates, is the most conspicuous change, aside from the size,
undergone during the first stage.
The First Molt. The first molt occurs from a month to six weeks
after birth during the summer months, and this may be prolonged to
two months or more during the winter season. There is considerable
variation in the time of molting, even though the scales be of the same
age, and under the same conditions. We have found this same fact true
for the cottony cushion scale, there being as much as two months differ-
ence in the time of development of individuals, hatched on the same day
and living under identical conditions. This may be partly due to pos-
sible differences in food supply, as well as to individual differences in
the scales themselves.
Development Between the First and Second Molts. The change
undergone after the first molt is not very striking aside from the begin-
ning of the formation of the letter H. At this time the ridge that forms
the bar of the letter extends from one end of the scale to the other.
Later the two ends become obliterated and after the second molt the true
H appears.
The Second Molt of the Female. This occurs on an average from
about two and a half to three months from birth, during the spring and
summer months. In winter this period may be considerably prolonged.
While there is more or less variation in the time of the first molt, under
the same conditions, there is still more variation with the second molt.
This molt brings the female scale to the adult stage.
Process of Molting. The process of molting in the black scale, like
other unarmored scales studied as Coccus hesperidum and Saissetia
hemisphaerica, consists of a splitting of the old skin at the anterior end
and then a pushing of this backward until it is free from the insect.
The ;east skin. which is a very minute frail object rolled up more or
less, may sometimes be caught still adhering to the posterior tip of the
body. But in breeding cages, sealed on the leaf with paraffin, we had
no trouble in detecting these after they were completely removed from
the body. Often times they look not unlike a film of cotton, and the
velvet which was first used in our cages to prevent the insects from
escaping, gave us much trouble in distinguishing the molted skins. The
antenna beak, legs and all other integumentary structures go with the
molted skin.
Effect of Temperature. The effect of high temperatures has already
been noted in the case of the active larvae. But even after that stage
they do not escape, and so, after the scales become fixed and have grown
to some size, hot weather periods are likely to kill them off in very large
numbers. A survey of the black-scale-infested territory a week or two



after one of these hot spells will show that in some cases almost the
complete generation is killed. Scales may, of course, be found dead in
considerable numbers without a well-defined hot weather period. But
the killing is much more pronounced and uniform after such a period
and it seems logical to attribute such a condition to it.
Honeydew and Fungus Growth. The excretion from the black scale,
when it falls upon the surface of the tree, offers a very suitable medium
for the growth of the sooty mold, Meliola camellia (Catt) Sacc. This
fungus is associated with all the other unarmored scales and also with
the insects of the families Aphididce and Aleyrodidce, as well as others
of less importance in the quantity of honeydew excreted. This fungus
is a saprophyte, and derives its sustenance from the honeydew. It is
not, therefore, directly injurious to the tree as a parasitic fungus would
be. Indirectly, however, it does do damage to the tree and especially
to the fruit, as previously explained. The characteristic black covering
formed over the plant is due to the vegetative threads of the fungus.
It is spread about from tree to tree by the agency of the wind in trans-
porting the spores.
Relation of Ants to the Scale. It very commonly occurs that trees
infested with the black, as well as other unarmored scales and particu-
larly the soft brown, will have ants running about over them. The ants
are there for the purpose of getting the honey as it is excreted by the
scales. The ants by a stroking with their antenna induce the scales to
give up small droplets which are immediately taken into their bodies.
The ants usually do no harm to the tree directly, unless they happen
to be nesting in large colonies about the roots. Occasionally they
do attack the tender growth, eating the tissues of the leaves and the
tender twigs. But indirectly the continual movement of many hun-
dreds of ants over the scales may tend to prevent oviposition by the
parasites of the scales. This is especially likely to be true in the case
of the Argentine species which infests the tree in such immense num-
bers. On the other hand, cases have occurred where the ants were
really a benefit. The chief injury, after all, in the case of the black scale
is in the honeydew and consequent sooty mold rendering unsightly and
unmarketable the fruit. Ants have been seen numerous enough to take
up all the honeydew just as fast as it was excreted and completely pre-
vent any sooty mold from forming on the plant surface.
Movement After Settling. As already explained, the young larva
settle largely upon the leaves. This is true also in the case of deciduous
trees. It is also true of such other unarmored scales as have a similar
life history, as the European Fruit Lecanium (Lecanium corni). In
the case of such scales on deciduous trees, they must migrate from the
leaves at some time because the dropping of the leaves in the winter


would prevent them from maturing. And so they do transfer them-
selves to the twigs as the leaves complete their growth in the fall and
become yellow and dry. Many also fall to the ground with the leaves.
and a large number of these must perish.
The same vital need for transferring themselves from leaf to twig
does not prevail in the case of the black scale on citrus trees. But it
is a fact, nevertheless, that only a very few adult black scales are ever
found on the leaves. There is, therefore, a transfer from leaf to twig,
since the majority of the young settle on the former. This occurs when
the scale is partly grown. The exact time varies greatly and is probably
dependent upon the food supply. In the case of the young first settling

Fm. 9.-Mature Black Scales.

it has been stated that the leaves are chosen because of the tissues there
being more easily penetrated and the liquid food nearer to the surface,
and thus more likely to be available through the short beak of the young.
On the other hand, as the scales become older and the beak larger and
stronger, they are more likely to get a greater supply of food from the
twigs, through whose tissues they are at this time able to penetrate.
But it may be an instinctive provision, too, to choose the more perma-
nent part of the tree for their final resting place. While a leaf on a
citrus tree may remain for two or three years, on the other hand it is
liable to drop off as in the case of a deciduous tree.
A drying of a leaf or some other abnormal condition will cause the
scales to loosen their hold and move about while they are still very
young, that is, before the first or second molt. But ordinarily the
greatest migration occurs later and after the second molt. This period
from settling, will thus be after three months and later. Scales have
been observed moving about when they had attained a length of 21 mm.
The smallest mature scales do not exceed this length, though they are, of



course, greater in height. Usually in the migrating stage they are still
elongate and not so broad as they become later. But many in the
so-called rubber stage have that broadened effect, and will be seen mov-
ing about looking for a suitable place to become permanently fixed.

After the second molt, which brings the female to the adult stage,
there is a very great increase in size, and also in general form. The
more or less elongate scale lying flat on the surface is now almost round,
and has become greatly thickened. The letter H is very distinctly out-
lined on the dorsal surface. As it approaches the egg-laying stage
many specimens become a dark mottled gray. When egg-laying is
begun, the scale takes on a more leathery, smoother surface and also
becomes much darker in color, this varying from a dark brown to a jet
The size of the adult varies from a height of 1 to 3 mm.; length, 2$
to 51 mm.; width, 2 to 43 mm. This represents about the extremes in
size, and individuals will be found at all sizes between these dimensions.
Usually on the same tree the majority of the scales will be of about the
same size. Nearly always on young, healthy trees the scales will be
vigorous and of good size. In other cases, and frequently on olive trees,
all the scales will be small. The condition of the tree, and the number
of individuals, appear to be the most important factors in determining
the size. Where the scales are simply crowded against one another, and
deformed for lack of room for normal growth, they are usually of small
Oviposition. Usually from eight to ten months are necessary to bring
the female to the egg-laying stage. The number deposited varies from
200 to about 3,000, with an average of 1,500 or 2,000. The oviposition
period lasts from six weeks to two months or longer.
On May 7, 1910, several solitary scales were selected on oleander
leaves and each enclosed with rings of tanglefoot. Young were issuing
from under them at the time, so that they must have begun egg-laying at
least 20 days previously. On the 31st of July young were still issuing
from under the adults. When these were overturned there were still
enough eggs to hatch for a week longer. The known egg-laying period
is thus 55 days, and the evidence points to at least 10 days longer. On
the 10th of August the last eggs hatched from one of these scales, mak-
ing a known length of 64 days, with possibly a week added on to this at
the beginning. A good healthy black scale will, therefore, deposit an
average of 30 or 40 eggs a day for a period of 60 days. If an egg-
laying female is removed from its natural resting place, it will continue
to deposit eggs for several days. The following table gives the results


of isolating egg-laying individuals in pill boxes to determine the extent
of oviposition when removed from their food plant. The scales were
taken from the twigs and all eggs removed on May 3d:

Oviposition When Removed from Food Plant.
No. May 4. May 5. May 6. May 7. May 8. May 9. May 10. May 11. May 12.
1 ------------ 30 72 122 152 ___ 303 315
S_------------- 36
3 -------- 62 106 183 254 __ 397 427
4 ---------- 64 148 218 300 340 -
-5 -50 98 138 195 275 480 510 648
6 --------- 163 244 362 510 627 ___ 00 824

While the black scale is very widely distributed over the world, little
has been known and practically nothing published about the male. It
was first described by Dr. B. W. Griffith* of Los Angeles in 1893. It
was thus said to be limited to a small area in the vicinity of Los Angeles.
During the past year or two we have taken it at various places in the
citrus belt from Santa Barbara to San Diego. It seemed to be especially
abundant during the season of 1909. In places where it occurred that
year, it was not nearly so abundant on the previous year or the year fol-
lowing. As many as 97 puparia, from all of which males had emerged,
have been seen on a single orange leaf. The males have been taken from
the leaves of orange, oleander, pepper and olive. They emerged during
the months of June, July, August, September, October, November,
December, and possibly other months, though not actually observed.
The Second Stage Male. Up to the time of the first molt there is no
difference between the sexes. After the first molt the male becomes
decidedly more elongate, resembling more nearly a partly grown soft
brown scale. Its length is 1.5 mm. and width .64. It is of a light brown
color with the eyes visible in the latter part of the stage as small dark
areas on the front margin. The anal plates together form a triangle
with rounded corners, and from the tip of each of these there arises
3 or 4 small spines, and one large one on the central dorsal surface.
The length of time spent in this stage is about four weeks. During
this time it is feeding and grows to about 5 times the length of the just-
hatched larva. At the end of the stage a puparium is formed which
completely covers the insect although it is transparent and not so
readily discernible.
The Male Puparium. This puparium is a glassy-like covering that
is formed from the secretion of numerous pores over the body surface.
Its length is 1 mm. and width .5 mm. The surface is slightly roughened
with a row of granular projections along the dorsal line. Two lines
beginning at the anterior end converge upward for a short distance and
then run more nearly parallel, with but a slight convergence toward the
*Ent. News, vol. XXII, no. 4, p. 167, 1911.



posterior end. Within this the surface is more convex, forming a ridge
along the dorsal line. Not quite one quarter of the distance from the
anterior end and at a point where the lines begin to run parallel, is a
cross line or carina. Another lateral carina crosses this dorsal strip, or
coronet, at one quarter the distance from the posterior end. Imme-
diately posterior to this cross line are two spiracular channels extending
to either margin. The other two spiracular channels, extending from the
coronet to either side, are just before the middle line. There is a
triangular opening for the anal plates and a cleft from this to the
posterior end. Along the margin is a series of circular pores from which
secretions extend to the surface of the leaf, thus holding the puparium
in place. When a puparium was removed 3 or 4 weeks after the male

I3I t

FIG. 10.-Development of the male of the Black Scale.
1. Second stage. 2. Propupa. 3. Pupa. x40.
had emerged, these connecting threads were still capable of being
stretched considerably as was observed upon lifting the puparium.
These are found usually on the under side of the leaves of the orange,
pepper, olive and oleander, chiefly, since these constitute the principal
food plants of the scale. When the insect is still beneath it can be
detected through this transparent covering. If it has not yet trans-
formed to the propupa it occupies the entire space beneath extending
well out to the margins, but in the case of the later stages the insect
beneath is somewhat narrower. These puparia may remain on the leaves
for months after the scale has emerged.
The second stage male is capable of moving up to the time the
puparium is secreted, which is the preliminary step in the change to
the propupa. But it is only rarely that any movement occurs in this


stage, and hence the males are nearly always found on the leaves where
the young first settle.
The Propupa. Length 1.4 mm., greatest width .4 mm. Color light
brown with red pigment scattered about, particularly at posterior end;
head reddish; eyes dark red or brown. Sheath of style short and blunt;
on either side of the style are two more slender and pointed appendages,
the cerci extending beyond the style. At the tip are a few short hairs or
spines. The sheaths of the antenna and legs are scarcely visible on the
dorsal surface excepting a broadening, where these lie on the ventral
margin. On the ventral side these are plainly visible, and lie in close
contact with the body. The length of the propupal period is from 5 to 8
days during the warmer weather.
iTe Pupa. Length 1.2 mm., width .4 mm., general color same as that
of propupa, excepting that there is a larger amount of pigment at the
anterior end. The head is entirely red. A marked constriction forms
the neck making the head appear as arrow-shaped. Eyes black. The
wing pads arc conspicuous and extend to third abdominal segment. The
style has increased in length so that it is slightly longer than the cerci
on either side. The antennae, legs and wing pads, while naturally lying
close to the body, are distinct and readily separated from it.
Eight to twelve days are spent in the true pupal stage, when it
changes to the adult. In all the molts after the second stage the skin is
split at the anterior end and pushed back beyond the puparium.
The Adult Male. The fully developed male remains from 1 to 3 days
beneath the puparium before emerging. The adult stage can be deter-
mined without the removal of the pu-
parium by the appearance of the long
white caudal filaments which project
out beyond the tip of the puparium.
The life of the adult male is from one
to four days. The following descrip- \
tion of the male is copied from the
notes of Prof. R. W. Doane, who
worked with the writer during the/ -'
summer of 1910: K !1
Length exclusive of style 1 mm.; '
style .4 mm.; caudal filament 8 mm.;
antennae 5 mm.; wing 1 mm. long,
.5 mm. wide; honey yellow; head
FIG. 11.-Male of Black Scale. x25.
darker yellow; anterior pair of upper
eyes dark red, posterior pair black, smaller; ventral pair black equal
in size to the upper anterior pair. Antennae whitish, 10 jointed, first
joint short, thick cylindrical; second joint about equal to first, but



oval; third joint about as long as second, but much more slender,
slightly swollen toward the tip; remaining joints all slender, cylin-
drical, fourth as long as fifth and sixth together; others subequal in
length, collar long, cylindrical; prothorax broad shield shaped; meso-
thorax more strongly chitinized and wholly brown except a yellow
shield-shaped area above, between the bases of the wings; metathorax
with a slight brownish tinge; legs brownish yellow; style yellow;
caudal filaments white, slender, tapering, twice as long as style; wings
hyaline with a yellowish tinge, with a microscopic close-set pubescence.
The above description is given in detail because the original descrip-
tion given by Dr. Griffith is incomplete. The only figures of the male
that have appeared from original specimens are given by Marlatt in
the United States Department of Agriculture year-book for 1900. "In
the figure of the adult there given the black bands are not properly
placed. Both are too far forward, the first is not broad enough, the
second too broad, and the yellowish spot between the wings does not
reach to the base of the wings.'-Doane.
When the males emerge the females that hatched at the same time
have completed their second molt, and the letter H is evident. Sum-
marizing the length of the life cycle of the male it will be during the
summer months as follows: 1st stage, 11 months; 2d stage, 1 month;
propupa, 8 days; pupa, 10 days; adult, 3 days; total, 96 days, or about
3 months.

Number of Generations. There is usually but one complete genera-
tion of the black scale in a season. The great majority of these come
to maturity in the spring months, so that most of the eggs are deposited
by midsummer. The time of maturing of the bulk of the black scales
will vary somewhat from year to year, and in some years there will be a
much more uniform hatch than others. Taking a specific season, as
1910 in the Los Angeles district, the height of egg-laying was during
the third week in May. The greatest production of young was about
the third week in June. Eggs will be deposited by a single scale during
a period of two months. By the middle of July, therefore, most of the
young had already appeared.
On June 3, 1910, sixteen different lots of young black scale were
distributed in twig cages on different orange trees. These remained
small throughout the summer, fall and winter, beginning to grow rapidly
in February and March, so that, when examined on April 26, 1911, some
had not yet begun egg laying, others had just started, while others had
been depositing eggs for a week or two. By the middle of May or first
of June, young were emerging from most of these scales. Practically
one full year was thus necessary to bring these scales from the period


of active young to the time when active young were in turn emerging
as progeny of these scales.
On March 15, 1911, a large number of active young were liberated
on a small potted orange tree that had first been fumigated and very
carefully inspected so that it was absolutely free from any scale. On
August 4, 1911, eggs were found under some of these scales which had
been liberated 44 months before. The scales were very small and were
probably stimulated to unusually early oviposition on account of the
scarcity of food, as the tree by this time was nearly dead. On August
10, young had commenced to hatch and settle making the period from
young to young approximately five months. This experiment verifies
what has been observed in the field, namely, that in the case of young
scales appearing very early in the spring they are very likely to com-
plete their development before the following winter.
On May 22, 1911, young black scales were liberated on small potted
pepper trees out of doors. When examined on September 8, 1911, 8 or
10 scales were found with eggs beneath. Counting the usual hatching
period the life cycle in this case would be completed in just four months.
The young hatching from the large spring brood in June and July
settle on the leaves largely, where they grow very slowly. Between a
month and two months the first molt occurs, and after an interval of
about the same length the second molt of the female occurs. This brings
it well into the fall, and from that time on migration occurs from the
leaves to their permanent abode on the twigs and branches. The winter
is passed as a partly grown insect. It has molted twice and is mature,
but is still of comparatively small size. With the first period of growth
of the citrus tree in the spring, and the rise in temperature, they grow
rapidly to full size, and are depositing eggs by the first of May. Those
scales, which hatch very early in the spring and have all of the warmer
period of the season to hasten their development, will mature in the fall
and thus complete their life cycle in a shorter time. The old scales die
very soon after their quota of eggs is deposited.
While the above history applies to the great number of scales generally
over the citrus belt, there is much variation in certain places as applies
to the bulk of the scales as well as to individuals scattered about every-
where, that are out of season with the majority. Their long period of
development, through which outside factors have an opportunity to
exert their influence, and the congenital differences within themselves,
as well as the artificial interference through fumigation must largely
account for this variation.
Mortality at Different Seasons. The season of greatest mortality of
the black scale is during the summer months, and particularly during
the hot weather periods. But the season alone is not responsible, for
the stage of the insect is equally as important. It is during the younger



stages that the great mortality occurs, and this, likewise, is in the
summer season. In another place it has been shown that less than 23
per cent succeed in getting established after hatching. Many in our
breeding cages died before they reached the first molt and the molting
period itself was a critical period when many more died. During the
time of development, therefore, or until they have transferred them-
selves to the twigs, there is much loss by death from one cause or
another. After they become fixed on the twigs there is comparatively
little loss of life. Such parasites as Aphycus flavus will attack them,
and there may be some loss by Coccinellids, but even these prefer the
scales in their younger stages. Even Scutellista, which attacks the
scale when it is mature, has no effect on the adult scale, for it confines
itself very largely to feeding on the eggs.
Annual Progeny of a Single Scale. While the total number of eggs
from a single scale may approach 3,000 in number, it is but an exceed-
ingly small per cent that ever reaches maturity. A tree having black
scale may become very badly infested in a single year. This is especially
true of well cared for citrus trees. It is also a common observation that
fumigated trees become reinfested more rapidly than one that has not
been fumigated. In many places trees infested with scale have never been
fumigated, and the number of insects present seems to remain almost
stationary. In such cases the number of the progeny only replaces the
number of the adults whose places they have taken. This is true gen-
erally of an insect after it has become established. In the case of a new
introduction, as, for example, the San Jose scale, Colorado potato beetle,
cabbage butterfly, and a host of others, the progeny that matured at
first was prodigious. But these insects after a few years, when they
become well established, have since maintained themselves in about the
same numbers, or, if anything, there has been a slight decrease.
So with the black scale where artificial control is not practiced the
actual progeny reaching maturity only replaces the parents. In case
of insects where the male is so rare as that of the black scale, this means
that only one, or at most two, of the total number of young produced
reach maturity. Of course, there may be yearly fluctuations, but for a
term of years it will hold true. An effort was made to determine the
actual progeny of the black scale under normal conditions. Ten small
olive trees were selected and on each of six there was a single black
scale, and on the remaining four there were two present on each. These
were examined 41 and 6 months later with the following result: On
tree No. 1 was one scale; on No. 2 no scale aside from the original one;
on No. 3 one; No. 4 and 5 two each; No. 6 no new scales; No. 7 three
scales; No. 8 two; No. 9 none; No. 10 one. If this experiment were
repeated a number of times there would probably be as many variations


as experiments, but the total together would result very much the same
as this single one, namely, that the progeny maturing would be approxi-
mately equal to the number of parents that gave them birth.

Scutellista cyanea Motsch.
The most important insect enemy of the black scale in this State is
Scutellista cyanea Motsch. It was introduced into the State in 1900 and
has since become well distributed in most of the sections where the scale
occurs in injurious numbers. The percentage of scales parasitized often
runs as high as 75 per cent, but this varies greatly in different sections
and in the same section in different years. In 1910 Scutellista was
abundant everywhere, but in 1911 it was unusually scarce. The year
1910 seemed to be the summit of one of its regular periods of increase.

In the autumn of 1895 Dr. L. O. Howard1 received specimens of what
later proved to be Scutellista cyanea Motsch, from Dr. A. Berlese at
Portici, Italy. These were bred from Ceroplastes rusci and it at once
occurred to Dr. Howard that it would be valuable to introduce the para-
site into this country to prey upon Ccroplastes floridensis, an injurious
scale in our southern States. It was not until 1898 that specimens were
received, and these were sent to Baton Rouge, Louisiana, where they
were distributed by Professor H. A. Morgan, as well as in the Insectary
at Washington by Dr. Howard himself. Both of these introductions
apparently failed.
A year later Mr. C. P. Lounsbury, government entomologist of Cape
Colony, found this species parasitic upon Lecanium olee, the common
black scale, and sent specimens to Washington for identification. To
quote Dr. Howard's own words2: "The past spring Mr. Lounsbury, at
the writer's request, made formally through the United States Secretary
of Agriculture to the Secretary of Agriculture of Cape Colony, brought
with him from Cape Town to New York two boxes of twigs covered with
black scale affected with this parasite, and expressed them to Washing-
ton, whence they were immediately forwarded to Mr. E. M. Ehrhorn,
the horticultural inspector of Santa Clara County, California. On
June 19th the writer received a letter from Mr. Ehrhorn announcing
the arrival in living and healthy condition of the parasites in question.
The twigs in one box were somewhat moldy, but quite a number of
parasites were crawling about in the box and were found in the pupal
condition in some of the scales. Mr. Ehrhorn had been warned by tele-
'Bull. 17. U. S. Bur. Ent., U. S. D. A., p. 13.
1Bull. 26. U. S. Bur. Ent., U. S. D. A., p. 17.
:{--BrIL. 223



graph and had prepared twenty-five infested oleander plants by potting
them and had covered each with a bag of Swiss muslin. In these most
of the parasites were liberated and a few allowed to fly in the orchard.
Specimens of a hyperparasite (Tetrastichus sp.) also survived the
journey, but Mr. Ehrhorn was on the lookout for this parasite and
isolated them as they appeared, pending instructions from Washington
as to their destruction.''
Economic Importance and Present Status in California. In spite of
the frequently high parasitization by Sculellista the black scale still
remains the most important citrus insect pest in the State. While the
number of scales may be considerably reduced through the work of
Scutellista, the standard of control required in the commercial citrus
orchard, which is clean fruit, is not often attained. This parasite being
an egg-feeder, it does not affect the generation of scales attacked. These
have done all the injury they would otherwise do, even though they had
not been attacked by Scutellista; unless the production of young, and
the consequent injury by them. is taken into consideration. Many
people realize that the parasite is present and doing good work entirely
on the basis of exit holes in the scales. This is. of course, the most con-
spicuous evidence, and does tell in a general way what is happening.
But the real test of what this parasite is accomplishing is to be found
in the ability to prevent young from appearing. With the maximum
number of exit holes there may still be an abundance of young settled
on the leaves. To the casual observer these often escape notice because
they are inconspicuous. That this number of young frequently runs
high may be indicated by the fact that from 400 to 700 young scales
have been counted on each of the leaves arising from twigs that had
75 per cent of the adult scales parasitized. If the efficiency of the
parasite in this case was to be judged solely on the number of exit holes
it would have been pronounced good, when as a matter of fact it was
of very little consequence. It might be said that there would have been
just that many more young had it not been for Scutellista; but in this
case no more could comfortably settle on the leaves. To follow this case
further, six months later there were very few black scales on the tree.
They had died during their early development, a good many before the
first molt and many more before the second molt. If the young had not
been seen on the tree earlier in the season the natural inference, con-
cerning the scarcity of the young scales as compared with the adults.
would have been that the Scutellista was responsible.
Such an instance as cited has been observed many times. And the
same thing happens where there are practically no Scutellista. The con-
clusion is forced upon us, therefore, that other factors, aside from this
parasite, are at work, and even though the parasite be present in large


numbers, it does not necessarily follow that it keeps the scale in check.
In such cases as mentioned above, the scales were all of large size, and
this has an important bearing on the efficiency of Scutellista. Where
the scales are small, and the maximum number of eggs produced may
not exceed 500, the Scutellista consumes them all, and is a very effective
check in reducing the progeny. On the other hand, where from 2,500
to 2,800 eggs are produced there are more than are necessary to bring
the Scutellista larvIe to maturity, and so many hatch and give rise to
young scales. On shade and ornamental trees the degree of control
effected by Scutellista may sometimes be sufficient, but this standard of
control is much less likely to satisfy the exacting demands of the com-
mercial citrus grower. But even on such shade trees as the pepper, the
infestation often becomes so severe as to warrant spraying, as was
generally done in the city of Los Angeles during the past year. While
the Scutellista should have full credit for the work it actually does, it
should not be counted the one effective agency for the control of the
scale whenever or wherever it is not injurious. In Santa Barbara
County practically no control work is done against scale insects on
citrus trees. In many places in the county the black scale is not
injurious. In other places it occurs in abundance, and there is much
evidence of sooty mold fungus. The Scutellista is no more abundant
there than elsewhere, and is even less abundant where the scales are not
injurious. So it is in smaller sections in other parts of the citrus belt.
Distribution of Scutellista. This parasite is generally distributed
throughout the citrus belt of southern California. It may occur much
more abundantly at certain times in some groves than others, but if
living scales are present and in the proper stage Scutellista will soon
be found infesting them. On this account the liberation of a few para-
sites in a grove will not greatly augment the numbers already present.
If there are sections that happen to be free from Scutellista, then arti-
ficial introduction will greatly aid them in becoming established. In
order that the introduction be effective they should be liberated at a
time when the scales are in the proper stage or shortly before. The
best season for this will be during May and June. A month earlier or a
month later will also find scales in the right stage, but usually in fewer
numbers. Scales will be found somewhere in the egg stage at all sea-
sons, but aside from the months mentioned, examination of the partic-
ular grove where the introduction is desired should first be made to
determine the condition of the scale.

The Egg. The egg of Scutellista is pearly white in color, oval, more
tapering at one end, from which arises an appendage or stalk. The
length of the body of the egg is about .4 mm. and the stalk varies from



one half to nearly twice that length. The one shown in the figure has
a stalk of the extreme length. This stalk is also straighter than others,
and there are many gradations from the nearly straight one shown to
those having a sharp double curve. The eggs are found beneath the scale
either among the eggs of the scale or on the central side of the insect
itself if the eggs are not yet present. Eggs have been found both in the
field and insectary under scales that had not yet reached the egg-laying
stage. Where they are present among the eggs of the scale they can be
distinguished from the latter by their slightly larger size and lighter
color. The duration of the egg stage during the summer months is
from 4 to 6 days.
The Larva. The young larva upon hatching from the egg is very
much like the mature larva excepting that it is smaller in size and
slightly longer in proportion to the width. The mature larva varies in
color from white to gray. The length of the average sized specimens is
about 3 mm. and the width 1 mm. It is broadest at the head end while
there is a gradual tapering toward the posterior end. The body consists
of 14 segments. The head segment is circular, disc shaped, in the center
of which is the mouth opening. The external mouth parts consists of a
pair of sharp chitinous hooks which are used for piercing the egg shell.
or the body wall of the scale itself if eggs are not present. Above and
laterad of the mouth on the same segment is a pair of short blunt spines
or horns.
The young larva upon hatching soon begins to feed on the eggs of the
scale by sucking out their contents, or if eggs are not present it attacks
the scale itself. Several instances have been observed where the larva
had grown to considerable size under a scale that had not yet laid eggs.
It is not, therefore, strictly an egg feeder, as generally supposed, but of
course eggs constitute the normal food. Larvm have been reared from
the soft brown scale (C. hesperidum) in which case no eggs at all were
consumed, for this scale lays no eggs. Larva have also been seen to feed
on others of its kind. Cases must occur in nature where several eggs of
the parasite are deposited under the same scale, but one, two, sometimes
three, and very rarely four, come to maturity. It is possible, therefore.
that this cannibalistic habit may occur more or less frequently in nature.
The amount of food consumed or the number of eggs necessary to
bring the larva to maturity varies greatly. A scale has not yet been
found too small to have a Scutellisia pupa. In the case of very small
scales it is possible that the larva feeds to some extent on the scale itself.
Where the larva appears before the egg-laying period, its attack on the
scale may be the cause of the scale being of small size, or of causing it
to deposit eggs before it is fully mature. The minimum number of eggs
laid by the black scale may be as low as 200 while counts have shown
the maximum to run above 2,800. The size of the mature larva will vary


greatly in these two cases and likewise the adult. Where the smaller
number of eggs occur they are all consumed, but with the larger num-
bers more than enough is necessary to satisfy the larva, and consequently
many hatch.
The full grown larva preliminary to pupation hollows out a cell in
the old egg skins and mats these together more or less with a small
amount of silk. Strands of silk are frequently, or usually, spun from
the inner edge of the scale to the twig, thus insuring the scale remaining
fixed during the pupal life of the parasite. It has been frequently
observed that old scale harboring Scutellista pupa are not lifted from
the twig so readily as those not parasitized. Black scale that have thus
been parasitized are more likely to remain longer on the tree than those
that are not. These may remain on the tree for two or three years in
many parts of southern California, where there are no extremes of
weather to dislodge them. This fact is not often taken into consideration
in estimating the amount of parasitization, so that scales with exit holes
increase with each year's infestation, while those without are more
likely to drop off.
Length of Larval Life. A larva just hatched was placed in a capsule
filled with eggs of the scale on July 19th, and allowed to remain until
pupation, which occurred on the 15th day. Others were reared under
similar conditions and the larval life was as follows: one larva 16 days;
another 17 days; another 20; another 21; and another 17 days. The
larval life may thus vary from 15 to 21 days, with an average of about
18 days.
The Pupa. When the pupa is first formed it is white in color like that
of the larva. But it soon begins to take on the darker color, and those
under observation changed to the jet black in about four hours. The
scutellum, eyes, and three small spots on front of head were first to
become dark, and later spots appeared on the abdomen. In two hours
the whole body had become a very dark gray, tinged in spots with the
characteristic metallic black. At this time the parts mentioned above
showed blackest, as did also the areas where the wings join the thorax,
and the edges of the abdominal segments.
The length of the pupa varies from 11 to 3 mm. The large scutellum
is conspicuous and extends to the posterior margin of the second abdom-
inal segment. The sheaths enclosing the wings, legs and antenna are
plainly visible on the ventral surface and the whole jet black in color.
Length of Pupal Life. On June 24th a larva pupated and was iso-
lated in the laboratory. The adult emerged in 18 days. Others in the
insectary, where conditions were nearly like out of doors, showed little
variation. The following records were obtained at different times, but
all during the summer months: 3 females in pupal stage 17 days;



3 females 18 days; 5 males and 6 females 15 days; 8 females 16 days;
2 females 17 days; 2 males 17 days; 1 female 16 days; 1 female 19 days;
3 females 18 days; 1 male and 2 females 19 days; 2 females 17 days;
I female 20 days. The minimum is thus 15 days and the maximum 20
days, with an average of 18 days for the pupal life.
The most unusual number of pupa found under a single scale is one.
but two are commonly found, and more rarely three, while four have
been observed twice in many hundred scales lifted. A scale with four
of these pupe is shown in plate V. It will be noticed that each is in a
separate cell, with the egg skins held together with silk, dividing them.

The adult is the familiar hump-backed blue fly-like insect which is
often seen walking slowly about among the scales. It is strikingly
different from any of the other Coccid parasites. The scutellum is very
long and extends well toward the tip of the body. The head is broad,
set closely into the thorax and is bent under, forming with the scutellum
a rounded arch. While the general color is metallic blue, the antenna
and tarsi, excepting the last joint, are usually light brown.
The adult upon transforming to the pupa eats out a circular hole in
the dorsal surface of the scale. This operation of eating its way out has
occupied from one to three hours in the cases that were kept under
observation. They are in the adult stage from one to three days before
emerging. This has been determined by fastening a scale to a cover
glass by means of glue, when the transformation to the adult could be
observed and the time of emergence noted. In lifting scales in the field
it will be noticed that occasionally an active adult makes its escape,
though no exit hole has been started. After emerging it is not a very
active flier and only occasionally indulges in extended flights. It
crawls about actively among the scales and when disturbed it jumps or
flies for but a short distance.
Oviposition. The eggs are inserted almost invariably under the arch
at the posterior tip. The ovipositor is thrust forward and backward
two or three times, the egg laid and ovipositor withdrawn, all within
about one half minute. The position of the insect in relation to the
scale is just opposite that of A. diaspidis of the red scale. In the case
of the latter the parasite is facing away from the scale, and the ovi-
positor is inserted by a pushing backward. With Scutellista the insect
is facing toward the center of the scale, and the ovipositor is inserted
by a pulling of the tip of the abdomen forward. Scutellista have been
observed to oviposit within twenty-four hours after emerging. It does
not always show the best judgment in selecting scales for oviposition.
Oviposition has been noted to occur under the old scales from which all
the young had hatched; also under scales already occupied by Scutellista


larva; under scales where not enough eggs remained to bring the larva
to maturity, and where the young had hatched but died before emerging.
Eggs have also been deposited under a scale where there was a larva of
Several eggs may sometimes be laid under the same scale, but this is
usually done by different individuals. The same insect will lay several
eggs in succession, but different scales are selected for each deposition.
In the laboratory a large number of eggs have been obtained under the
same scale. Twenty or twenty-five mature females were confined in a
test tube with a single partly grown black scale and more than fifty
eggs were found beneath it a day or two later. So many were deposited
that the scale was lifted from the twig. In such a case they were
inserted at other points than the arch at the posterior end. But it will
be noted upon consulting plate II that even here the majority were
inserted at the posterior end. Oviposition has been noted to occur
naturally in the field under scales that had not yet reached the egg-
laying stage. In the insectary the youngest scales chosen were those
that had recently molted the second time. They were thus mature, but
were still very small and would not normally deposit eggs for several
months later. But this was under forced conditions, and such young
scales would probably not be selected in the field. Young scales pre-
vious to the second molt were not chosen even under forced conditions.
About 50 female Scutellista were confined in a tube enclosing an
oleander leaf on which were black scales about one month old. A day
or two later an examination of the scales failed to reveal any eggs having
been deposited. On a check experiment with mature scales eggs were
oviposited under freely.
Proportion of the Sexes. In a considerable number of specimens col-
lected at different times the number of males and females do not vary
greatly, but in general the males are slightly in the majority. This
seems to be especially true where the scales themselves are small. The
size of the Scutellista varies greatly and this is dependent upon the food
supply. The males are, of course, smaller than the females, but whether
the food supply has any influence on sex determination is a debatable
subject, with the greater amount of more recent evidence against it.
Parthenogenesis. While males are nearly always present in equal
or even larger numbers than females, reproduction is apparently able
to occur without the males, according to the following experiment.
Mature black scales with eggs were allowed to remain a week under
cover in order to allow any chance for Scutellista eggs that might be
present to hatch. In the mean time several pups were put each in a
separate box and the adults allowed to mature. Two of these unfertil-
ized females were placed in a vial containing a twig infested with a
single hlnck scale. Seven days later the scale was lifted and two Scutel-



lista eggs and four larve were found. Since the eggs hatch in from
four to six days the larva and eggs present must have come from those
Length of Adult Life. A young orange tree badly infested with black
scale was placed in a screen cage and several Scutellista of both sexes,
which had just emerged, were liberated. The conditions were as nearly
natural as possible, there being ample opportunity for oviposition, or
for feeding, if necessary.. The length of life under these conditions was
10 to 15 days. Others which had recently emerged were confined in pill
boxes without food. The length of life was about the same as under the
above conditions.
By spraying sweetened water on scale infested twigs in the laboratory
Mr. P. H. Timberlake and Mr. Rust have succeeded in keeping tho adults
alive for from 23 to 51 days.

The stages and abundance of Scutellista are very much dependent
upon the same conditions in its host. Since the black scale is at the
height of egg laying in June, it is then that Scutellista larva will be
most abundant. The pupal period follows this and July will usually be
the period of greatest emergence of adults. While in June and July
the various stages of Scutellista are most abundant, it will be found to a
less extent in all stages at all other seasons. Just as there are scales
out of season so there are of their parasites. But during the off season
the Scutellista, like the scales, may not be found in the same grove.
They may be on other trees than citrus, such as pepper, olive. or
oleander, or they may be on citrus trees in a different section. or even
a different grove, where conditions may be more or less different.

Here again the scale determines largely the number of generations.
If there were a uniform hatch of the scale occurring during the
spring and no more scales matured until the same time next year, there
would be but one generation of Scutellista. Since, however, some scales
may be found in all stages at all seasons, the Scutellista is permitted to
go through several generations. The number will thus vary, but when
the scales are in the right stage the number can be calculated from the
length of life cycle. One record from egg to adult will indicate the
length of life and the duration of the different stages.
Egg laid July 22d; hatched July 27th; pupated August 12th; adult
emerged August 26th; adult died September 4th. The egg period
is thus 5 days, larval 16, pupal 15, adult 9, or a total of 45 days from
the egg to the death of the adult. Another completed its life cycle in
43 days; another in 45 days; another in 50 days; another in 48 days;


another in 44 days; another in 46 days, and another in 50 days. On
this basis there would be 4 generations from May to October, inclusive.
From November to April, on account of the slower development during
the winter months there will be from 2 to 3. While there may be
thus a total of 6 or 7 generations a year, on account of the unfavorable
condition of the host. 4 or 5 will be nearer the actual number.

Cerchysius sp.
Under the old black scales there will be occasionally found, instead of
the characteristic Scutellista pupa, a black or brown oval or torpedo-
shaped body that may at first be mistaken for a dipterous puparium.
This will be found to be the old larval skin of the Scutellista larva dis-
tended and harboring a parasite within this parasite. This has been
taken from several different sections, including Whittier, Glendale.
Pomona, Santa Paula, and Santa Barbara. But it is found most abund-
antly at Santa Barbara, where in certain groves the percentage of Scu-
tellista attacked ran between 5 and 10 per cent.

The larva of this hyperparasite is white in color, length 2 mm.,
greatest width nearly 1 mm., 13 segments, broadest at head end and

S, ,

FIG. 12.-Hyperparasite on the Scutellista, Cerchysius sp.

gradually tapering toward the posterior. Very similar in color and
shape to that of its host. On the head segment of the larva of Scutellista
there is present above, and laterad of the mouth, two blunt horns or
spines. These are absent on the larva of Cerchysius. This larva com-
pletely consumes the contents of the Scutellista larva, leaving only the
outside epidermis. This is changed to a leathery texture, and to a dark



brown or black color. Preparatory to pupation the meconia are voided,
and these are to be found compressed into one end of the larval skin of
the host. Scutellista larvm attacked by its parasite, and having the char-
acteristic appearance as though the parasite within was in the pupal
stage, were collected on October 29th, and upon removing the covering
on December 31st the hyperparasites were present as full grown healthy
larvae. From this it would appear that the full grown larva must pass
through a period of hibernation, or else the effect on the host is made
evident very early, or at the beginning of the attack by the parasite.
Nearly all the host larve were full grown when they took on the char-
acteristic appearance of parasitized larve, but a few have been taken
when they were but one half grown. Occasionally the host manages to
change at least partially to the pupa. In such cases certain characters
of the pupa appear, as the constriction at the head, the large scutellum
and the outline of the abdomen, but there are practically no indications
of appendages or other characters of the true pupa. Specimens from
which the parasite appeared ready to emerge, which were collected in
October, were still in the larval condition in January, indicating that
the winter or at least a portion of the winter is passed as a full grown
The pupa appears to change within -its old larval skin, as shown in
plate VI. This was removed from a parasitized Scutellista larva at the
same time that the full grown larvae were taken.

Length 1- mm.; wing expanse 3 mm. Head and thorax finely reticu-
late and covered with fine black hairs. Entire body black, with greenish
iridescence; front leggs entirely black; middle femur with band of light
brown at proximal one third, lighter color at tip of femur, and greater
area at tip of tibia; middle tarsi light brown. Hind legs entirely black;
tibial spurs present, middle ones largest. Tarsi 5 jointed. Antenna
10 segmented, pedicel widened in center and twice as long as first seg-
ment; joint 3 equal to 1, remaining joints of equal length, excepting last.
This segment, which is club-like, is divided into three divisions. The
segments, excepting first two, are covered with many hairs nearly equal
in length to that of the segment. Wings not fringed or with very short
hairs. Sub-marginal vein strong and with row of conspicuous spines.
When the adult is ready to emerge a cap or portion of one end of the
larval skin of the Scutellista is broken off and after emerging from this
eats out a circular hole in the dorsum of the scale similar to the Scutel-
lista. excepting that they appear very slightly smaller on the average.


Tomocera Californica How.
This is another egg parasite of the black scale, and formerly was as
abundant as Scutellista is to-day. In 1880 Professor Comstock stated
that "upon more than one tree at least 75 per cent of the scales appeared
to be parasitized. In no locality was the black scale found without this
attendant destroyer." During the past three years this same parasite
has been but occasionally met with. So scarce has it been that we have
not secured enough material to make it worth while undertaking life
history studies. It seems to be most abundant at present in Santa
Barbara County and possibly were we on the grounds there some
material might have been available for life history work. What has
changed this from a very abundant parasite to one only rarely met with
is difficult to account for. It would involve a thorough study of the
inter-relations of all the factors bearing on the subject. Again, some
definite and specific cause, such as the usurping of the field by Scutel-
lista, might account for it. What was true regarding the abundance of
Tomonrrc in 1880 was true for Scltellista in 1910.

According to Comstock the female pierces the body of the scale and
deposits probably but a single egg. It is more likely that, like Scutel-
ii.,a. the ovipositor is inserted between the scale and the twig. The
mature black scale, with its
tough. leathery surface.
would not be easily pene-
trated by the ovipositor, and
it might also result in injury .
to the scale.
The larva feeds upon the. ....
eggs and young, and to some
extent on the scale itself if
eggs are not present. When
full grown it is about 4 mm.
long, broad, spindle shaped,
somewhat more pointed at
the anterior than the poste- F1G. 13.-Tomocera californica How. From
Report U. S. D. Agr. for 1880.
rior end of the body. Its
color is clear white, the contents of the alimentary canal often showing
through, giving it a blackish tinge. This larva transforms to a whitish
pupa which soon turns black, in this respect again being similar to
Scutellista. The same sort of an exit hole and of the same size is made
in the scale.
The adult, in general color, is a metallic blue black insect. Enough of

F, u-iiE, i 2'23|


Howard's original description' is given herewith to enable identification.
Length of body 2.1 mm.; wing expanse 3.5 mm.; abdomen subovate, first
segment large. On each side of the peduncle on the anterior part of the
first abdominal segment is a strong tuft of snow white hairs. Head,
face, scape of antenna, and under side of all legs, light mahogany
brown. Thorax black with a strong metallic luster on prothorax, tip of
scutellum and scapulm, abdomen bluish black with a slight brownish
patch beneath at the base. Tarsi 5 jointed. The center of the forewing
is occupied by a large dusky patch.

Aphycus Flavus How.
Aphycus flavus How. is parasitic upon the male black scale. Speci-
mens of this parasite have been taken at Whittier, Glendale. PI'imona,
and San Diego. It attacks the male scale in the second stoai- and is
strictly an internal parasite. It also attacks the female at about the
time for the second molt.
The larva is a small, white, grub-like creature, measuring when full
grown about 1 mm. long and I mm. broad. It is the broadest near the

VI'. 14.-Aphyeus flavus How. parasite of soft brown
and other scales. x40.
head end and tapers gradually toward the posterior end. The man-
dibles are very broad and stout, abruptly tapering into a sharp, slightly
curved hook. The curved tip will distinguish it from the larva of
A. diaspidis.
The pupa is darker in color, having changed from the white color of
the larva. Its length is 8 mml. and greatest width mm. The ee ar

The Adult. Length 1.2 mm.; wing expanse 2 mm.; color dark yellow,
abdomen darker; eyes reddish black; antennae scape with dusky patch
'U. S. D. A. Report, 1880, p. 368.


above; wings clear; veins yellowish; antenna 11 jointed; pedicel about
twice as long as thick. The club is as long as the three preceding joints.

Aside from those already mentioned, Coccophagus lecanii and C.
lui ulatus have been reared from the partly grown scales. But all of
these internal parasites are very scarce as compared with the egg-feed-
ing parasites.
According to Mr. C. P. Lounsbury, the following parasites have been
reared from the black scale by Mr. C. W. Mally in South Africa:
Scutellista cyanea Motsch.
Coccophagus oricntalis How.
Microterys sp.
Microterys sp.
Coccophagus, near ochraceus How.
Aphycus lounsburyi How.
Tetrastichus sp.
Tetrastichus sp.

1. 2. 3.

Fwi. 15.-Coccinellids feeding on the Black Scale. x5.
I. Olla plagiata Casey.
2. Axion plagiatom Casey.
3. Orcus chalybeus Boisd.
4. Larva, pupa and adult Rhizobius ventralis Black.

IB LLFIjYs 223]


Rhizobius ventralis.
The commonest and most characteristic Coccinellid attacking the black
scale is Rhizobius ventralis. The larva feeds on the eggs, the young that
have not emerged from beneath the parent, and the younger stages of
the insect after it has settled. On account of its firm leathery covering,
the adult is seldom attacked by this beetle.
The egg is pearly white in color and oval in shape. Its length is .8 of
a millimeter and its width .4 mm. They are found under the scale.
Plate II, figure 3 shows five such eggs in their natural position beneath
the black scale. Eggs are not laid here exclusively, for this beetle feeds
on other insects than the black scale. And sometimes even with this
scale eggs may be deposited elsewhere, but they are very commonly
found under the scale.
The Larva. Length 5 mm.; width 11 mim.; upper surface entirely
black; prothorax segment surrounded on margins, except posterior, with
a row of long hairs, those laterally arising from prominences. A row
of short inconspicuous hairs on either side of the dorsal line, two hairs in
a place, papille scarcely visible. Another row slightly more than one
half way to lateral margin, from two to five hairs on each segment, and
arising from prominent papillae. Another row slightly below lateral
margin with six hairs in a place arising from very conspicuous pro-
tuberances. Ventral surface dirty gray with legs darker in color.
The larva hatching from those eggs laid under the scale begin to feed
on the scale, or the eggs, or young. In case the scale is in the egg-laying
stage they may grow to considerable size under the same scale, and
wander about attacking many different scales. It is in this stage that
the most feeding is done and consequently is most efficient as an enemy
of the scale.
The Adult is broadly oval in shape, measuring about 3 mm. long.
Thorax and elytra shining black and covered with gray hairs. The
surface is finely punctuate; ventral side of head and thorax black.
Abdomen distinctly brown. Legs black, excepting the tarsi, which are


Orcus chalybeeus.
This is the steel blue beetle that is found commonly on citrus trees.
particularly in Santa Barbara County. It has been more frequently
met with on black scale infested trees than any others.
Several other species of Coccinellids have been taken from black scale
infested trees, including Hippodamia convergents, Coccinella californica,
Chilocorus bivulnerus, and Axion plagiatom.



V-IG. 16.-First and second stages of some unarmored scale insects.
1 and 4. Saissetia oleae Bern.
2 and 5. Coccus hesperidum Linn.
3 and 6. Lecanium corni Bouche.



Hemispherical Scale.
(Saissetia hemispherica Targ.)
This only rarely becomes troublesome
Sn citrus trees, but occurs commonly on
ornamental and greenhouse plants. Its
lighter color, glossy surface, smaller size, P
and the absence of the letter H will read-
ily distinguish it from the black scale.
The common parasites are Comys fusca
and Coccophagus lecanii.

Soft Brown Scale.
(Coccus hesperidum Linn.)
This scale frequently attacks citrus
fruit and a few trees or parts of trees are
often badly infested. Its flatness and
lighter color distinguish it at once from
the black. The earlier stages, however,
resemble the black very closely. Some of
the differences are shown in the accom-
FIG. 17.-Hemispherical Scale
paying figures. Aplycus flavus, En- on twig of orange.
cyrtus flavus, Coccophagus lecanii, and Coccophagus lunulalts. are the
commonn parasites of this scale.

Fo. 1 8.-Soft brown scales with exit holes of
Aphycus flavus.

Photograph of small orange tree in the field showing Black Scale on
trunk and branches.


1. Different stages of Black Scale.
2. Young Black Scale shortly after settling.
2. Eggs of Rhizobius ventralis under Black Scale. x17.
4. Hemispherical scale on left and black of same size on right.
5. Inverted Black Scale with 50 eggs of Scutellista. x30.


PLA..\T 111.
1. Black scale with exit hols of rS'utellista.
2 Portion of same more enlarged.
3. Young black scale 1i;tlcr d bu t died before emerging.
4. Eggs and young scales killed by fungus, Tsaria.

1. Male puparia of Black Scale. xli.
2. Same enlarged. x18.
3. Puparia of HemisphEerical Scale. Same magnification as 2.

Scutellista cyanea Motsch, egg x70; larva x25; pupme, ventral and dorsal
views x20; adult x17 ; inverted Black Scale showing four pupe; exit holes
in scales.


1. Larva of Soutellista parasite, Cerehysius sp. x25.
2. Larva of Cerchysius partly changed to pupa. x25.
3. Parasitized lJirva of Scutellista lharboring Cerchysius within. x25.
4. API)eiarance- of parasitized Seutellista larva beneath scale. x25.
5. Normal Seutellista pupa. x20.
6. Parasitized Scutellista pupa or Scutellista larva which succeeded in pm
changing to pupa. x20.
7. Exit hole of parasite in old larval skin of Scutellista.
8. Black scale killed by fungus, Isaria.
9. Fungus covering scalo and spreading over twig.


sz. A,




Photomicrographs of derlm pores. x50.
1. Saissetia oleae Bern.
2. Saissetia hemispherica Targ.
3. Lecanium corni Bouch6.
4. Lecanium pruinosum Craw.
5. Lecanium sp. on Heteromeles.
6. Coccus hesperidum Linn.

- BJ

Leaf on right showing sooty mold fungus as a result of Black Scale infes-
tation. Normal leaf on left.

A---- Mi ---A-

Saissetia olese on Olive.


-.- 'C\.- -- ,, *

-A .

FIG. 19.-Encyrtus flavus How. 9 x25.

European Fruit Lecanium.
(Lecanium corni Bouch).)
This is what has been called the brown apricot scale in this State and
went by the scientific name of Eulecanium armeniacum Craw. Pro-
fessor J. G. Sanders' in a recent study of the Lecanium group places it

/ -

FIG. 20.-Coccophagus lunulatus How., parasite of soft brown and
0 other scales.

under the name given above. This scale does not occur on citrus trees,
so far as we have seen, but is frequently associated with the black on
prune, apricot and other deciduous trees. Comys fusca is the com-
monest parasite and is widely distributed.

'Jour. Ec. Ent., vol. 2, No. 6. p. 443.




FIG. 21.-Antennue and anal lobes.
1. Saissetia oleae Bern.
2. Lecanium pruinosum Coq.
3. Coccus hesperidum Linn.
4. Lecanium corni Bouche.

The Frosted Scale.
(Lecanium pruinosum Coq.)
This scale is very similar to L. corni and frequently occurs with it
as well as with the black. It is usually considerably larger than corni
and is covered with pruinose, hence the name. In southern California
it not infrequently occurs on the English walnut. Comys fusca has also
been reared from this scale.

Lecanium sp.
This scale occurs very commonly on the Christmas berry Heteromeles.
It was at first mistaken for the Hemispherical scale, but typical speci-
mens appear much larger and slightly different in shape. Upon drying
they are also inclined to shrivel, as indicated in the figure. It is very


FIG. 22.--L!CLniun Sp. 1n HeleruomeleS.

/$~iL -

49 &


FIG. 23.-Comys fusca How., parasite on Hemispherical, Brown Apricot,
and other scales. x18.






heavily parasitized by Coimys futsca and to a less extent by Coccophagus
lecanii. The former attacks only the larger scales, and since these come
to maturity in May and June this is the time when most of the parasites
emerge. Scales attacked by C. fusca do not lay eggs. While C. lecanii
usually attack the smaller scales, not infrequently the larger ones are
also chosen. One or two of these parasites may mature in the scale and
yet eggs will be deposited by the scale.

.. .

FIG. 24.-1. Larva of Comys fusca. 2. Pupa of Comys fusca.
3. Pupa of Coccophagus lunulatus.

Saissetia oleae Bern. belongs to the subfamily Coccin, of the family
Coccidce, which is characterized by the possession of triangular supra-
anal plates. This species is readily recognized by a median longitudinal
carina and two transverse carina forming the characteristic H. Other
species of the genus recorded from California are: filicunt Bvd., hemis-
phc3rica Targ., and nigra Mitn. Aside from hemispharica these species
are limited to a greenhouse locality and are of no particular importance.
The species olece was first described under the genus Chiermes. A few
years later it was placed under the genus Coccius. In 1852 the name
Lecanium. was given for the genus and for a long while it was thus
known by various writers until it was changed by Professor Cockerell to
Saissetia in 1901.



Up to 1903, the bibliography of Saissetia oleae is given in Fernald's
Coccidai of the World. The following includes the references to this
insect since 1903, which has been furnished through the courtesy of
MAr. E. R. Saccer, of the Bureau of Entomology, Washington.

Saisettia oleae Bern.

Reh, Dr. L.: Zeitschr. f. Entom. VIII, pp. 418-419. Nov. 1, 1903.
Bibliography, food plants, etc.
Theobald, F. V.: 1st Rept. Ec. Ent. Br. Mus., p. 140 (1903).
Coleman. G. A.: Journ. N. Y. Ent. Soc. XI, p. 82. June, 1903.
Coleman, G. A.: Journ. N. Y. Ent. Soc. XI, p. 74. June, 1903.
King. G. B.: Ent. News. XIV, p. 205. June, 1903.
Thro. W. C.: Bull. 209. Cornell Univ. Agr. Exp. St., p. 214, pi. IV; figs. 1-3;
pl. V. fig. 8. Jan. 1903.
Ehrhorn. E. M.: 1st Bien. Rept. of Com. Hort. Sta. Cal. 1903-04. p. 111.
Stiftz. A.: Jahr. d. Pflanz. (1904.) p. 137.
Kirkaldy, G. W.: The Entomologist, vol. XXXVII, Sept. 1904, p. 228.
Green, E. E.: The Coccide of Ceylon. Part III, p. 227 (1904).
On Antidesma bunius, Grewia orientalis, Duranta, Thespesia populnea, Cajanus
Dickel, Dr. O.: Zeit. f. wiss. Insekt. Heft II. Bd. I, Nov. 20, 1905, p. 447.
Simpson, C. B.: Transvaal Dept. Agric. Ann. Rept. of Director. 1904-1905, p. 350.
Cockerell, T. D. A.: Proc. Davenport Acad. Sciences, vol. X. 1905.
Del Guercio: Boll. Uff. del Min. d'Agr. Indust. & Comm. V. 3, p. 262 (1906).
Records Tomocera californica, Coccophagus sp. and Scutellista cyanea as para-
Tyrrell. Mary W.: Rep. Agr. Exp. Sta. of the Univ. Cal. Year 1894-'95, p. 265.
Plates II, III, IV.
Herrera, A. L.: Bol. d. 1. Com. de Parasitologia Agric. Tomo III. num. I (1906).
Ehrhorn, E. M.: The Can. Entom. Vol. XXXVIII. No. 10, Oct. 1906, p. 332.
Gahan, A. B.: Bull. 119 Md. Ag. Exp. Sta. July, 1907. pp. 11-12, fig. 4.
Ehrhorn, E. M. : 2d Bien. Rep. Com. of Hort. Sta. of Cal. 1905-'06. pp. 23 and 223.
Carnes, E. K.: 2d Bien. Rep. Com. Hort. Sta. Cal. 1905-'06 (1907), pp. 193-194.
Paoli. Berlese An. & Am.: "Redia," vol. IV, Fasc. I, pp. 48-80. 4 figs. (07.)
Figures illustrating various stages of L. oleae, as well as those of its predaceous
and parasitic enemies.
Green. E. E.: Trans. Linn. Soc. of London. Vol. XII, part 2, Dec. 1907, p. 200.
Reported from Chagos Is., Aldabia, Mauritius, Europe, N. Z., Australia, China,
Japan, Java, H. I., S. Africa, Ceylon, Brazil, W. Indies, Mexico, U. S. A.
Newman, L. J.: Jn. Dep. Ag. of Western Australia. Vol. XV, part 12. Dec. 1907.
p. 914.
"Reduced to a harmless scale in this state by its introduced natural enemies."
Froggatt, W. W.: "Australian Insects" (1907), p. 370.
Autran, E.: Bol. del Min. di Agr. Vol. VII. No. 8, p. 151, 1907.
Howard. C. W.: Transvaal Ag. Jn. Vol. VI, No. 22, Jan. 1908. p. 274.
Froggatt. W. W.: The Jn. of Agr. of Victoria. Vol. VI. pt. 5, 8th May, 1908, p. 277.
Lea, A.: Insect and Fungus Pest of Orchard and Farm. Tasmania, 3d edition, p. 64.
Pease. S. A.: 34th Fruit Growers' Convention Sta. of Cal. (1908.) p. 40.
Lounsbury. C. P.: Rep. of Gov. Ent. Year 1907. Cape of Good Hope, Dep. Agr.
Cape Town. 1908.
Cook, A. J.: Off. Rep. 34th Fruit Grow. Con. of Cal. p. 50. Sacramento. 1908.
Ehrhorn. E. M. : Proc. of 33d Fruit Grow. Con. of Cal. p. 151. (1908.)



Cook, M. T.: Bull. No. 9. Estacion Central Agron. de Cuba. Feb. 1908. p. 26.
fig. 34.
Froggatt, W. W.: The Jn. Dept. of Ag. of So. Australia. Vol. XII. No. 1. Aug.
1908. p. 38.
Martinelli, Dr. G.: Bol. di Lab. di Zool. General e Agraria. Vol. 11 (1908)
pp. 217-20.
Descr. fig. hosts and parasites.
Newman, L. J.: Jn. Dept. of Ag. W. Australia. Dec. 1908. Vol. XVII p. 942.
Cook, M. T., & Horne, W. T.: Bull. No. 9. Estacion Central Agron. de Cuba.
Feb. 1908. p. 26. fig. 34.
Lindinger, L.: Zeit, f. wiss. Insektenbiol., v. 5, p. 224 (1909).
Essig, O. E.: Pomona Jn. of Entom. Vol. 1, No. 1. March, 1909. pp. 12-15. fig. 9.
Carnes, E. K.: 3d Bien. Rept. Com. Hort. Cal. p. 25. (1909.)
Dean, Geo. A.: Trans. Kans. Acad. of Sciences. Vol. XXII. p. 269. (1909.)
Sanders, J. G.: Jn. Econ. Ent. Vol. II. No. 6. p. 440. pi. 20. fig. 2. Dec. 1909.
Severin, H. C., & H. H. P.: Jn. Econ. Ent. Vol. II. No. 4. p. 297. Aug. 1909.
Newman, L. J.: Jn. Dept. Agr. W. A. XVIII, 7, p. 500 (1909). Fig.
Fullaway, D. T.: Hawaii Agr. Exp. Sta. Bul. 18. p. 16. (1909.)
Pestana, C.: Bull. Agricole de l'Algierie et de la Tunisie, No. 6, 15, March, 1909.
pp. 146-48.
Brick, C.: Sta. fur Pflanzenschutz zu Hamburg, X, p. 11. (1909.)
Garcia, N.: Bol. Agr. Tech. y Econ. 1, No. 3. p. 268. (1909.)
Brick, C. : Sta. fur Pflanzenschutz zu Hamburg, XI, p. 6. (1909.)
Kirk, T. W., & Cockayne. A. H.: Ann. Rep. Dept. Agr. Div. Biol. & Hort. ). 285.
Doane, W. R.: Can. Ent.. xli, 8, p. 297. (1909.)
Barber, T. C.: Jn. Econ. Entom. Vol. 3, No. 5, p. 424. Oct. 1910.
Knischewky: Zeit. fur Pflanzenkrankheiten, Band XX, Heft. 5, p. 267. (1910.)


Report of the Viticultural Work during the seasons 1887-93, with data regard-
ing the Vintages of 1894-95.
Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viti-
cultural Report for 1896.
Report of the Agricultural Experiment Station for 1898-1901.
Report of the Agricultural Experiment Station for 1901-03.
Twenty-second Report of the Agricultural Experiment Station for 1903-04.


Reprint. Endurance of Drought in Soils of
the Arid Region.
No. 128. Nature, Value, and Utilization of
Alkali Lands, and Tolerance of
Alkali. (Revised and Reprint,
133. Tolerance of Alkali by Various
147. Culture Work of the Sub-stations.
149. California Sugar Industry.
151. Arsenical Insecticides.
152. Fumigation Dosage.
153. Spraying with Distillates.
159. Contribution to the Study of
162. Commercial Fertilizers. (Dec. 1,
165. Asparagus and Asparagus Rust
in California.
167. Manufacture of Dry Wines in
Hot Countries.
168. Observations on Some Vine Dis-
eases in Sonoma County.
169. Tolerance of the Sugar Beet for
170. Studies in Grasshopper Control.
171. Commercial Fertilizers. (June
30, 1905.)
172. Further Experience in Asparagus
Rust Control.
174. A New Wine-cooling Machine.
176. Sugar Beets in the San Joaquin
177. A New Method of Making Dry
Red Wine.
178. Mosquito Control.
179. Commercial Fertilizers. (June,
180. Resistant Vineyards.
181. The Selection of Seed-Wheat.
182. Analysis of Paris Green and
Lead Arsenic. Proposed In-
secticide Law.
183. The California Tussock-moth.
184. Report of the Plant Pathologist
to July 1, 1906.
185. Report of Progress in Cereal In-
186. The Oidium of the Vine.
187. Commercial Fertilizers. (Janu-
ary, 1907.)
188. Lining of Ditches and Reservoirs
to Prevent Seepage and Losses.
189. Commercial Fertilizers. (June,

No. 190. The Brown Rot of the Lemon.
191. California Peach Blight.
192. Insects Injurious to the Vine in
193. The Best Wine Grapes for Cali-
fornia; Pruning Young Vines;
Pruning the Sultanina.
194. Commercial Fertilizers. (Dec.,
195. The California Grape Root-worm.
197. Grape Culture in California; Im-
proved Methods of Wine-mak-
ing; Yeast from California
198. The Grape Leaf-Hopper.
199. Bovine Tuberculosis.
200. Gum Diseases of Citrus Trees in
201. Commercial Fertilizers. (June,
202. Commercial Fertilizers. (Decem-
ber, 1908.)
203. Report of the Plant Pathologist
to July 1, 1909.
204. The Dairy Cow's Record and the
205. Commercial Fertilizers. (Decem-
ber, 1909.)
206. Commercial Fertilizers. (June,
207. The Control of the Argentine Ant.
208. The Late Blight of Celery.
209. The Cream Supply.
210. Imperial Valley Settlers' Crop
211. How to Increase the Yield of
Wheat in California.
212. California White Wheats.
213. The Principles of Wine-making.
214. Citrus Fruit Insects.
215. The House Fly in its Relation to
Public Health.
216. A Progress Report upon Soil and
Climatic Factors Influencing
the Composition of Wheat.
217. Honey Plants of California.
218. California Plant Diseases.
219. Report of Live Stock Conditions
in Imperial County, California.
220. Fumigation Studies No. 5; Dos-
age Tables.
221. Commercial Fertilizers. (Octo-
ber, 1911.)
222. The Red or Orange Scale.





No. 1. Texas Fever.
5. Contagious Abortion in Cows.
7. Remedies for Insects.
9. Asparagus Rust.
11. Fumigation Practice.
12. Silk Culture.
15. Recent Problems in Agriculture.
What a University Farm is For.
19. Disinfection of Stables.
29. Preliminary Announcement Con-
cerning Instruction in Practical
Agriculture upon the University
Farm, Davis, Cal.
30. White Fly in California.
32. White Fly Eradication.
33. Packing Prunes in Cans. Cane
Sugar vs. Beet Sugar.
36. Analyses of Fertilizers for Con-
39. Instruction in Practical Agricul
ture at the University Farm.
46. Suggestions for Garden Work in
California Schools.
48. Butter Scoring Contest, 1909.
49. Insecticides.
50. Fumigation Scheduling.

No. 52. Information for Students Concern-
ing the College of Agriculture.
54. Some Creamery Problems and
55. Farmers' Institutes and Univer-
sity Extension in Agriculture.
58. Experiments with Plants and Soils
in Laboratory, Garden, and Field.
59. Tree Growing in the Public Schools.
60. Butter Scoring Contest, 1910.
61. University Farm School.
62. The School Garden in the Course
of Study.
63. How to Make an Observation Hive.
64. Announcement of Farmers' Short
Courses for 1911.
65. The California Insecticide Law.
66. Insecticides and Insect Control.
67. Development of Secondary School
Agriculture in California.
68. The Prevention of Hog Cholera.
69. The Extermination of Morning-
70. Observations on the Status of
Corn Growing in California

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