Official Organ of the Florida Entomological Society
VOL. XX OCTOBER, 1937 No. 2
THYSANOPTERA OF THE GEENTON
(Continued from No. 1, Page 15)
J. R. WATSON
Hoplothrips (Trichothrips) wilsoni sp. nov.
Female (apterous): Length about 2.9 mm. (some over 3 mm.) ; color
yellow brown, prothorax and apical abdominal segments somewhat darker;
head brownish-yellow; legs somewhat lighter yellow; tube grayish yellow
in apical third, shaded with brown in basal two-thirds; abdominal seg-
ments five to seven, bordered posteriorly with darker transverse bands;
antennal segment two and basal half or more of three, concolorous with
the head, segment one shaded darker especially at base, 4 to 8 blackish-
brown, 4 a 'shade lighter than the others. Hypodermal figment orange
by reflected light, maroon by transmitted light.
Head a trifle longer than broad. Dorsum faintly striated at the sides.
Cheeks slightly arched, quite strongly converging posteriorly, abruptly
widened behind the eyes where they usually bear one or two small spinose
tubercles. Postocular bristles pale, slightly curved, and long (152 microns),
extending far beyond the eyes, pointed at tip, a small bristle between
the base of each antenna and the eye. No other prominent bristles on
the head. Eyes small, usually showing but 4 or 5 facets in lateral out-
line, dark. Mouth cone short and broadly rounded, reaching but little
over half way across prosternum. Antennae about twice as long as
head; segment one, oblong in outline, sides nearly straight and converging
but slightly apically. Segment two, barrel-shaped apically, at about two-
thirds the distance from the apex abruptly contracted (especially on the
outer margin) to a broad pedicel, bent sharply outward; 3 to 5 clavate,
broadest about one-fourth the distance from the apex and from there
gradually converging to a broad base; 6 and 7 barrel-shaped, more abruptly
contracted to narrower pedicels; 8 conical, abruptly contracted to a nar-
row, short pedicel. Sense cones colorless and stout; those on segments
6 and 7 are especially long and stout (about 26 microns long). Bristles
also very pale.
Prothorax about as long as the head, and (including coxae) nearly
twice as broad as long, smooth. A moderately long bristle on each anterior
angle, and two pair of minute ones along the anterior margin. Dorsal
and median to the latter is a pair of somewhat larger ones. A pair of
long (152 microns) bristles on each posterior angle, the outer of these
strongly curved. A somewhat shorter bristle on each coxa is bent sharply
forward at about the middle and again backward near the end; a few
THE FLORIDA ENTOMOLOGIST
short bristles scattered over the dorsal surface of the prothorax. All
bristles pale yellow; pointed at tip.
Mesothorax somewhat narrower than the prothorax (including coxae);
sides nearly parallel but diverging slightly posteriorly. Legs rather short.
Fore femora much enlarged. Fore tibia with a pair of thick short anter-
iorly directed lobes at the apex on the inside. (These are appreciably
smaller than those shown in the figure of the male.) Fore tarsus with
a large, slightly curved tooth which is considerably longer than the width
of the tarsus.
Fig. 1.-Male of Hoplothrips (Trichothrips) wilsoni n. sp.
(Drawing by L. S. Maxwell)
Abdomen thick and heavy, widest at about segment two from which
it is gradually rounded to the base of the tube. Bristles near the posterior
angle of segment nine 200 microns long. Tube nearly as long as the head.
VOL. XX-No. 2 19
Sides straight in apical two-thirds but somewhat swollen in basal third.
Six pair of terminal bristles; the dorsal laterals 187 microns long. The
dorsal mediads are only about a third as long and pale yellow. The ventral
mediads still shorter and colorless.
Measurements of type: Total body length 2.9 mm.; head, length
.30 mm., greatest width (immediately behind eyes) .27 mm.; prothorax,
length .30 mm., width (including coxae) .56 mm.; mesothorax, greatest
width .54 mm.; abdomen, greatest width .71 mm.; tube, length .26 mm.,
width at base .102 mm., at apex, .047 mm. Antennae, total length .59
mm.; segments, length (breadth): I, 59 (54); II, 70 (40); III, 102 (40);
IV, 94 (41) ; V, 78 (35); VI, 70 (30); VII, 59 (29); VIII, 51 (23) microns.
Female (macropterous): Appreciably smaller than the apterous fe-
males. Color darker, especially the head which is concolorous with the
prothorax, dark brown. Tube and especially the legs more heavily shaded
with brown, only fore tibia and tarsi brownish yellow. Only basal half
of antennal segment III brownish yellow; other segments dark brown,
II a shade lighter.
Head fully as wide as long in the type, but some paratypes have the
head shape more nearly approaching that of the apterous females. Much
less abruptly swollen behind the eyes and usually without the spinose
tubercles. Dorsum more conspicuously striated than in most of the apterous
females. Eyes large, occupying about .4 of the lateral outline of the
head, finely faceted. Ocelli large, light yellow, bordered by dark red
irregular, blotch-like crescents. Posterior pair situated about opposite
the middle of the eyes and contiguous with their margins.
Wings short, membrane reaching to about the seventh abdominal seg-
ment, shaded lightly with gray, closely fringed with rather short hairs,
from 13 to 16 accessory ones on the fore wings.
Measurements of type: Total body length 2.6 mm.; head, length
.23 mm., greatest width .24 mm., at base .21 mm.; prothorax, length .26
mm., width (including coxae) .44 mm.; mesothorax, width .45 mm.; abdo-
men, greatest width .61 mm.; tube, length .26 mm., width at base .096 mm.,
at apex .047 mm. Antennae, total length .62 mm.; segments, length
(width): I, 58 (52) ; II, 70 (35) ; III, 105 (46); IV, 101 (44); V, 84 (35);
VI, 74 (32); VII, 65 (26); VIII, 59 (20). Postocular bristles 128, outer
ones at posterior angle of the prothorax 133; terminals of the tube 210
Male (apterous) (Figure 1): Body yellow brown, similar to that of
the apterous female but head, fore legs, the second antennal segment and
basal half of third usually much lighter yellow.
Head (excepting the tubercles) usually narrower, especially posterior-
ly, but in some males approaches in shape that of the female.
Tubercles very variable in size. In some (Fig. 1) very large, in
others minute or entirely lacking. Posterior to this large tubercle there
are often two or three smaller ones. The most posterior one about the
middle of the cheek.
Reticulations on the dorsum more conspicuous than in the female,
near the base forming a net-like structure. Frons clouded with brown
as is antennal segment I, especially at the base.
Prothorax a third longer than in the female. Fore femora often
greatly enlarged, much larger than the head. But this characteristic is
THE FLORIDA ENTOMOLOGIST
very variable, in many males being scarcely at all enlarged. The spur
at the apex of the lower surface of the tibia larger than in the female,
concolorous with the tibia and with it an additional spur, larger, pointed,
and much darker in color.
Measurements: Total body length 2.7 mm. Head, length .30 mm.;
width across tubercles .27 mm., at base .19 mm.; prothorax, length .42
mm., width (including coxae) .56 mm.; mesothorax, width .54 mm.; abdo-
men, greatest width .66 mm.; tube, length .21 mm., width at base .09 mm.,
at apex .04 mm. Antennae, total length .65 mm.; segments, length
(breadth): I, 84 (47); II, 75 (37); III, 112 (41); IV, 103 (37); V, 85
(35); VI, 73 (28); VII, 58 (28); VIII, 59 (20) microns. Postocular
bristles 140; those at posterior angles of prothorax 136; terminal 170.
Nymph: The life history of the insect has not been worked out but
four rather definite sizes were collected in addition to the pupae and
prepupae. The first two differ markedly from the third and fourth in
the shape of the antennal segments and probably represent different
Length about .6-.7 mm. Color brownish gray with much orange
hypodermal pigment. Last abdominal segments lighter. Eyes red by
reflected light, black by transmitted. Antennae nearly half as long as
the head; seven-segmented. Segments I-VI about as wide as long.
Length about 1.0-1.1 mm. Last two abdominal segments darker,
light brown. Antennal segment I gray; II-V darker gray; VI and VII
brown. Antennal segments about the shape of those in above; VII conical,
more than three times as long as wide; IV the largest.
Length 1.3-1.8 mm. Color light grayish brown with much bright
crimson hypodermal pigment, often arranged in transverse bands across
the abdomen. Terminal segment of abdomen grayish yellow, the next
deeply shaded with brown. Head with straight parallel sides. Segments
I and II of antennae mostly concolorous with the head; II shaded with
brown at the base; III-VII dark brown; III with a brownish yellow
pedicel; III-VI elongated, club shaped; VII cylindrical (37 microns long),
subequal to VI, rounded at end. Total length .35 mm. Eyes very small,
Length 1.7-2.2 mm. Color yellowish brown with red hypodermal pig-
ment arranged as in the last. Last two segments of abdomen darker
brown. Head small; .19 mm. and .15 mm. wide. Frons rounded with
two slightly curved bristles projecting forward half as long as the head.
Antennae as in the previous ones.
Prepupa 1.4-2.1 mm. long. Color light brown, head wider than long,
(.25 :.21 mm.). Eyes black.
Pupa: Uniform yellowish brown with red hypodermal pigment.
Described from sixty apterous and eighteen winged females,
thirty-two males, and numerous nymphs collected by Dr. J. W.
Wilson and the author, between November 17, 1935 and March
31, 1936 from the trunk of a silk oak tree, (Grevillea), infected
with Diplodia rot and exuding much gum, at Leesburg, Florida.
The insects were all associated with the gum from the rot.
VOL. XX-No. 2
J. D. Hood has called the author's attention to the close rela-
tionship of this species to his calcaratus described from Trini-
dad, (Psyche, 1925, p. 57). This species can be readily distin-
guished from calcaratus by its larger size and much darker
color, the much longer and sharper spine on the fore tibia, (in
calcaratus this is triangular in shape), and many other char-
Adraneothrips pallidus (Watson)
In 1924 (Fla. Ent. VIII, p. 50) the author described this
insect under the name of Gastrothrips ? pallidus. In the fol-
lowing year Hood (Psyche, XXXII, p. 54) established the genus
Adraneothrips. To that genus this species evidently belongs
since the wings are constricted in the middle as in Haplothrips
but do not broaden again apically but remain narrow to the
tip. This genus is evidently a large one in the American tropics.
Many species have been described and the writer has several
more taken mostly from banana refuse. This thrips is the most
hydrophilous of those of the geenton, being the most abundant
species in moulding leaves in low swampy hammocks just above
the water level and in Spanish moss on trees. It has also been
taken from Tillandsia on trees, Polyporus gilvus and Chiodecton
rubrocinctus on the bark of trees. It has been taken from Lloyd
(only a few miles from the Georgia state line) to Key West
and on a lemon from Cuba.
Eurythrips batesi (Watson) and E. reticulatus (Watson)
Mr. Dudley Moulton has called the writer's attention to the
characters which place these species described under Glypto-
thrips (Fla. Ent. XVIII, p. 45-46, 56-57) in the genus Eury-
Printing for All Purposes
Delivered on Time
Pepper Printing Company
We recommend the goods advertised in The Florida Ento-
mologist. Please mention Entomologist when you write our
Official Organ of The Florida Entomological Society,
VOL. XX OCTOBER, 1937 No. 2
J. R. WATSON, Gainesville-.........-.......-...................-------....- Editor
E. W. BERGER, Gainesville...-....--....-..-...------.....--Associate Editor
J. W. WILSON, Lakeland --...-.........----.......--......Business Manager
Issued once every three months. Free to all members of the
Subscription price to non-members is $1.00 per year in ad-
vance; 35 cents per copy.
ADDITIONAL NOTES ON NAUPACTUS LEUCOLOMA
J. R. WATSON
Since the article in the last number of the FLORIDA ENTO-
MOLOGIST (Vol. XX, No. 1) was published, some further obser-
vations have been made on this insect, which will be recorded
The adults, which began to emerge about the middle of June,
apparently reached their maximum numbers about the 10th of
July. During this month two trips were made to the infested
region and observations made on the habits of the adults.
One of the most surprising discoveries at this time was made
by Dr. A. N. Tissot of this department; namely, that no males
are produced. This, however, is not unique in this group as a
Russian entomologist, Silantjev, has recorded similar phenomena
in a related genus. It does, however, immensely increase the
danger of its being carried into uninfested sections, since but
a single female or even a grub might start an infestation.
In mid-July the adults are distinctly shade lovers. During
the middle of the day they are found in places protected from
the sun. On the cotton plants most of them crawl to near the
terminal bud where they are well shaded by the upper leaves.
When infesting peanuts they crawl down to near the base of
the plants, where they receive some shade from the stems. Late
in the afternoon, earlier if it is cloudy, the adults leave the
shade and begin to crawl actively over the ground, laying their
eggs at the same time. Some were observed to crawl at the
rate of about four feet per minute.
VOL. XX-No. 2
The eggs are laid in the ground, if it is not too hard. Other-
wise many of them are laid on sticks and stones and other
materials. They are surrounded by a gelatinous material to
which numerous grains of sand adhere, so it is very difficult
to distinguish the eggs in the soil. The eggs are oval in shape,
about one-sixteenth of an inch long, and somewhat less in width.
They are yellow in color.
The preferred foods of the adults are somewhat more re-
stricted than are those of the larvae. Peanuts, beggarweeds,
cockleburs and cotton seem to be favorites of the adults. A few
were feeding on Passiflora, and still fewer on the so-called
"Mexican clover" (Richardia). None were observed on corn,
cane or other grasses. However, if the corn, which was ap-
proaching maturity, had been young and tender it might have
In some fields the weevils were extremely numerous. Some
workers in the U. S. Bureau of Entomology estimated that
there were as many as 400,000 per acre in some fields. Although
the adults do not seem to be hearty feeders, they nevertheless
in many fields had entirely exhausted their food plants and
migrated to other fields. The amount of damage that they can
do and their migratory habits are illustrated by the history of
two fields, adjacent to each other, on an infested farm.
One field was planted to peanuts in 1936 and, according to
the County Agent, was a "complete loss". When this field was
visited in May of this year it had again been planted to peanuts,
and the grubs in this field were extremely scarce. On the con-
trary, in an adjoining field of corn they were extremely abun-
dant-so much so that in one section of this field, about four
acres in extent, not a single ear was produced, and only a few
suckers were left standing. By the middle of July the ground
in this field was peppered with the exit holes of the adults, but
very few adults were found in this field. There had been a
heavy migration back to the peanut field first mentioned, where
the beetles were actively laying eggs. Doubtless if no control
measures are taken the history of 1936 will be repeated in this
field-the peanuts will be a total loss. The reason that there
were so few larvae to be found in this field in May of this year
is evidently because the larvae had destroyed all the host plants
in this field and forced the adults to migrate to the field planted
this year in corn where they laid their eggs, and this year they
did likewise to the corn and migrated back to the peanut field.
THE FLORIDA ENTOMOLOGIST
They are clumsy creatures and are utterly unable to climb
out of a furrow a few inches deep, providing the sides are dry
and crumbly. County Agent Wilkins was the first to notice
this characteristic and to suggest catching them in furrows
plowed around the infested fields. This measure has been
adopted by the Bureau of Entomology, since they have taken
charge of control measures in the infested territory. If post
holes are dug every few feet along the bottoms of the furrows
they are even more certain to capture the beetles.
The insects evidently spend the winter in the grub stage,
as farmers state that in plowing as early as December they
turn up numerous grubs. This observation has been verified
by Professor W. B. Gurney, New South Wales, Australia. In
a letter to the writer he states that the "Winter is passed in
the larval stage".
Professor Gurney also reports that this insect has been
found in only one locality in New South Wales. "Up to the
present the weevil has only been recorded at Willow Tree on
the Northern table-lands 250 miles north from Sydney. It is
not known how it was introduced, nor how it reached Willow
Tree, which is so far inland from Sydney, without becoming
established in other localities closer to Sydney. No detailed
studies of the pest have been made, but the adult weevil lays
its eggs by inserting the tip of the abdomen into the soil. The
larvae feed upon the tap roots of lucerne, sometimes completely
severing it, but more often making deep furrows along the
It is thus seen that its history of introduction into New
South Wales parallels that of Florida and Alabama, in that it
appeared at an inland station many miles from any port through
which it was probably introduced, though it has been recently
found about Gulfport and Laurel, Mississippi.
It was observed that chickens and hogs are very fond of
the beetles. Doubtless guineas and turkeys would be equally
so, and because they roam farther afield, would be more ef-
fective in their control. However, as abundant as these beetles
were in some of the fields it would take very large numbers of
poultry to effect anything like a thorough clean up.
The observations made this summer on the insect indicate
that we have here a very dangerous pest to the agriculture of
the entire south, and probably southwest since in Australia it
is a pest of Alfalfa. The insect in the larval stages feeds greedily
VOL. XX-No. 2
on the majority of the common crops in this section, and it will
certainly be difficult to raise a spring crop next season in fields
where the beetles have been abundant this summer.
PROGRESS REPORT ON DUSTS CONTAINING ROTENONE
FOR THE CONTROL OF FLEA BEETLES ATTACKING
SHADE-GROWN CIGAR-WRAPPER TOBACCOS
By F. S. CHAMBERLIN and A. H. MADDEN
United States Department of Agriculture
Division of Truck Crop and Garden Insect Investigations
Bureau of Entomology and Plant Quarantine
From information obtained thus far it appears that dust
mixtures containing rotenone have established their value in
combating flea beetles upon shade-grown cigar-wrapper tobacco,
especially the types of tobacco grownin northern Florida, south-
ern Georgia, and the Connecticut Valley. In the Georgia and
Florida producing region the crop is attacked by the tobacco
flea beetle (Epitrix parvula F.), while in the Connecticut Valley
the potato flea beetle (E. cucumeris Harr.) is the attacking
species. While dust mixtures made from ground derris root
will apparently exert a control quite similar to that of cube root
powder, the latter material thus far has been used almost
exclusively in investigational work and in commercial control
operations, owing to its lower cost.
The advantages of rotenone dust mixtures.-The three main
advantages of the rotenone-bearing dust mixtures made of cube
powder over the insecticides used previously to control flea
beetles on shade-grown cigar-wrapper tobacco are speed of action,
safety to the crop, and absence of objectionable residue, com-
bined with a relatively high toxicity to the insect. A quick kill
of flea beetles is essential in the case of wrapper tobacco, where
the leaves are the marketable part of the crop and where even
a few small holes detract from the value of the cured product.
The rotenone dust mixtures meet this requirement to a greater
extent than any of the materials utilized previously for flea
beetle control. Safety to foliage is a most exacting requirement
for an insecticide to be used in the culture of wrapper tobacco.
Any insecticide that has a tendency to burn, bleach, or discolor
the leaves to a noticeable degree is automatically eliminated
from further consideration. The question of residue on the crop,
THE FLORIDA ENTOMOLOGIST
resulting from insecticidal applications, is likely to assume even
greater importance in the future.
The disadvantages of rotenone dust mixtures.-The outstand-
ing disadvantage of this material is that its efficiency is of short
duration under the conditions imposed in tobacco shades. Dur-
ing the month of May 1936 a limited series of experiments
designed to show the deteriorating effect of sunlight upon cube
was carried out with three samples of dust mixtures containing
1.5, 1, and 0.5 percent of rotenone, respectively. Each dust
mixture was applied carefully to the foliage of a different half-
grown potted tobacco plant in such a manner that a very light
film of the material was visible upon the leaf surface. The
plants were kept beneath a cloth tobacco shade from 8 a. m. to
5 p. m. each day of the exposure period, with the exception of
a few short rainy periods, at which times they were removed
to a closed shed. They were also placed within the closed shed
each night to protect them from the washing effect of dew or
Immediately after the dust applications had been made, one
half of a 12-inch leaf was removed from each of the three treated
plants and from an untreated check plant. These leaf parts,
each containing approximately 40 square inches of leaf surface,
were placed within large lantern globes protected from direct
sunlight. One hundred tobacco flea beetles (Epitrix parvula F.)
were then introduced into each cage. Forty-eight hours later
the beetle mortality was determined in each of the cages.
Similar-sized leaf parts were removed from each of the plants
after exposure to the sun for 24, 42, and 50 hours, respectively,
and the toxicity of the dust-mixture residue was determined in
the manner just described. The results of these tests indicated
that the cube dust mixture containing 1 percent of rotenone
exerted a 74 percent kill of the flea beetles after an exposure of
24 hours to sunlight, which was about the equivalent of 2 days
of cloudless exposure. This work also indicated that the dust
mixture containing 1.5 percent of rotenone maintained its
toxicity much longer than the 0.5 percent material.
From the information now available it appears probable
that the effectiveness of cube dust mixtures containing 1 percent
of rotenone is limited to about 3 days under field conditions.
The value of cigar-wrapper tobacco, however, is comparatively
high, and frequent applications of the poison are justified in
order that the flea beetles may be controlled.
VOL. XX-No. 2
Cube is not toxic to grasshoppers and it exerts only a very
limited control of the tobacco hornworms (Protoparce spp.) and
the tobacco budworm (Heliothis virescens F.). Applications of
paris green, which are made occasionally to shade-grown tobacco
for flea beetle control, aid materially in the control of the above-
mentioned pests.1 The outstanding disadvantage of paris green,
however, is the burning hazard which attends its use even under
the most favorable conditions. Barium fluosilicate, which is used
frequently and is effective in controlling flea beetles upon newly
set tobacco, is also very effective in controlling grasshoppers
on the young plants.2 The use of this insecticide upon large
wrapper tobacco is hazardous, however, since it may cause burn-
ing of the leaves under certain weather conditions.
Dilution of cube root powder and dosage rates.-Preliminary
field tests conducted during 1934 and 1935 indicated that a cube
dust mixture with a rotenone content of approximately 1 percent
is effective in controlling flea beetles on cigar tobacco. During
1936 additional data were obtained from an experiment per-
formed in a 11/3-acre shade of tobacco grown under contract
by the North Florida Experiment Station, to determine the
relative toxicity to the tobacco flea beetle of three cube dust mix-
tures containing 0.5, 1, and 1.5 percent of rotenone, respectively.
The dust mixtures were applied by a hand duster to individual
plots, 69 feet wide by 50 feet long, arranged as a Latin square.
Each treatment was replicated three times and a series of four
untreated check plots was included. Previous experience has
shown that counts of living or dead flea beetles made within
the dense growth of a tobacco shade are of questionable accuracy.
For this reason the effectiveness of the three treatments was
determined from the percentages of beetle-injured leaves. This
work was facilitated greatly by spreading the cured sample
leaves in a moist and pliable condition upon a large glass plate
which was illuminated from below. Five applications of the
dust mixtures were made during the season, at the rate of 7
pounds per acre per application. No attempt was made in this
experiment to obtain a complete control of the beetles, since
a sufficient degree of feeding was desired so that significant
comparisons could be made. The applications of the insecticides
1CHAMBERLIN, F. S., and TENHET, J. N. 1923. The tobacco flea beetle
in the southern cigar-wrapper district. U. S. Dept. Agr. Farmers' Bul.
1352. 9 pp., illus.
2CHAMBERLIN, F. S. 1933. Barium fluosilicate as a control for the
tobacco flea beetle. Jour. Econ. Ent. 26 (1) :233-6.
THE FLORIDA ENTOMOLOGIST
were delayed, therefore, until the progeny of the over-wintered
beetles had emerged from the soil.
The results, which are given in Table 1, show that relatively
light applications of a cube dust mixture exert a marked con-
trolling effect against the tobacco flea beetle. They also indicate
that dust mixtures containing 1 and 1.5 percent of rotenone,
respectively, exert a greater controlling effect upon the insect
than a dust mixture containing 0.5 percent of rotenone. The
data should not be construed, however, as indicating the neces-
sity of using dust mixtures containing 1.5 percent of rotenone,
since it is possible that commercial control may be obtained with
material of lower rotenone content applied at the proper inter-
vals. Until additional data are obtained it seems desirable to
continue the present recommendations of a 1 percent rotenone-
bearing dust mixture for the control of flea beetles upon shade-
grown cigar-wrapper tobacco.
TABLE 1.--THE PERCENTAGE OF TOBACCO LEAVES INJURED BY FLEA BEETLES
WHEN TREATED WITH DUST MIXTURES CONTAINING VARIOUS PER-
CENTAGES OF ROTENONE.
Rotenone content of dust mixture Injured leaves
Percent Mean percent
Rotenone dust mixtures appear to kill flea beetles principally
because the irritating properties of this insecticide impel the
beetles to "clean up" after coming in contact with it. Dosages
of this insecticide should, therefore, be sufficient to give good
coverage of the plants. For newly set tobacco plants a dosage
of 4 or 5 pounds per acre should be sufficient, while in the mature
crop a dosage of 8 to 10 pounds per acre is believed necessary.
Choice of diluent.-Finely ground Georgia clay, kaolin, or
diatomaceous earth may be used as the diluent for cube root
powder when the dust mixture is to be applied to newly set
tobacco. The application of these white-colored materials to
the maturing crop may, however, cause a discoloration of the
cured product. Experiments have shown that finely ground
tobacco dust is a satisfactory diluent for use on cigar-wrapper
VOL. XX-No. 2
tobacco, and it leaves no discoloration. While the addition of
a small proportion of clay to the tobacco dust may improve its
physical qualities, the quantity of clay added should not be
sufficient to change perceptibly the brown color of the tobacco
dust. Tobacco dust used for this purpose should be certified
by the manufacturer as being sterilized and free from pathogenic
organisms which might spread tobacco diseases.
Time of day for applications.-While positive proof is not
yet available, the writers are of the opinion that cube dust
mixtures should be applied to cigar-wrapper tobacco early in
the morning, late in the afternoon, or in the evening (Fig. 1).
Weather conditions are usually most favorable for efficient dust
applications during these hours of the day and the dust mix-
ture appears to be more effective under moist than under dry
conditions. Growers in the Florida area have found this true
in practice and frequently apply the dust mixture to their
tobacco crops immediately after a light rainfall. The safety
of the material under these critical conditions is in marked
contrast to the insecticides formerly used to combat flea beetles.
Since maturing shade-grown tobacco is frequently damp for a
large proportion of the day, the safety of rotenone-bearing dust
mixtures under these conditions is a great advantage.
Fig. 1.-Applying cube dust mixture to maturing shade-grown cigar-
wrapper tobacco for the control of the tobacco flea beetle.
THE FLORIDA ENTOMOLOGIST
IMPORTANCE OF BEES IN THE PRODUCTION
Most varieties of watermelons are monoecious, the pistillate
and staminate flowers being borne in separate axils of the leaves.
In a few varieties, however, there may be hermoproditic and
staminate flowers. As with many of our crops, these flowers
are pollinated chiefly if not altogether by bees. They, therefore,
are a very necessary factor in the production of a melon crop,
and the number of them and their activity may directly de-
termine the size of the yield of melons. This seems to have
been well illustrated at Groveland, Florida, during the 1935
season. At that time a number of growers had planted their
melons in adjacent areas so that an almost solid block was
formed of around a thousand acres. Along the margins of
this area there was a much better set of melons than in the
central portion. Near the edges two or three acres produced a
carload of melons while in the center of the area 4 or 5 acres
were required. Dr. M. N. Walker visited this area, and after
checking over the possible causes, concluded that the difference
was probably due to the fewer number of bees reaching the
central portion of the field.
In the Leesburg section during the 1937 season a collection
was made of the bees visiting melon flowers, and sent to Dr.
Grace Sandhouse for identification. Below is a list of the species
in the order of their abundance in the melon fields.
Apis mellifica Linn6
Halictus (Chloralictus) nymphalis Smith
Halictus (Chloralictus) lepidii Graen
Halictus ligatus Say
Halictus (Chloralictus) apopkensis Robt.
Augochlorella gratiosa (Sm.)
Agapostemon splendens (Lep.)
Augochloropsis caerulea (Ashm.)
The honey bee was by far the most abundant species. The
next three species listed occurred fairly abundantly while the
others were much less common. A visit to a field near Lees-
burg and one near Groveland on successive days showed that
there was probably ten times as many bees in the first field. In
this last area a rather poor set was obtained in some commercial
fields and the lack of bees was probably the reason.
The honey bee is the first to make its appearance in the
VOL. XX-No. 2
mornings. About the middle of May the first bees observed
at the flowers were seen usually between 6:45 and 7:15 a. m.
Bees of all types reach their greatest abundance in the field
around 8:30 or 9:00 a. m.
From these observations it is quite evident that the size of
the melon crop may be greatly influenced by the bees. Observa-
tions in Florida and elsewhere show that certain days are favor-
able for setting melons while a very poor set will occur on other
days, due to weather conditions. If the favorable days are few
and the supply of bees small, the yield may be small.
A factor which is of great importance in Florida is the need
of producing an early crop. By far the greatest portion of
the crop is shipped to the northern states, and the prices are
usually the highest during the first week or two. When the
melon crop is ready to ship from the other southern states, Flor-
ida is at a disadvantage due to the longer shipping distance.
It is, therefore, important that a good set be obtained from the
earlier flowers and to insure this an adequate supply of bees
should be present. Thus, in certain areas at least, the earliness
and size of yield may be increased by keeping honey bees near
the field during the flowering season. In large fields best re-
sults should be obtained by having a hive near the center of
the field. C. C. GOFF
INDEX TO THE FLORIDA ENTOMOLOGIST
An index to volumes 1 to 19 inclusive of the Florida Ento-
mologist is now in preparation. This index contains a table of
contents arranged by volumes and an index of the insects by
specific and varietal names. This index is to be sold at 75c a
copy. Orders should be sent to J. W. Wilson, Business Manager,
Lakeland, Florida. Subsequent volumes will have an index in
the last number of each volume.
FLORIDA ENTOMOLOGISTS WILL BE INTERESTED IN
Synthetic Contact Insecticide
The killing agent in this new type of spray is an organic thiocyanate.
Lethane 440 has shown itself to be outstanding for the control of
cottony cushion scale, mealy bugs and other scales; red spiders and
mites; white fly, leafhoppers, thrips and aphis. For information
ROHM & HAAS COMPANY
222 West Washington Square Philadelphia, Penna.