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THE SOUTHERN BEET WEBWORM.







BY


F. H. CHITTENDEN, Sc. D.,
In Charge of Truck Crop and Stored Product Insect Investigations.






ISSUED NOVEMBER 11, 1911.





















WASHINGTON:
GOVERNMENT PRINTING OFFICE.
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U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF ENTOMOLOGY-BULLETIN No. 109, Part II.
L 0. HOWARD. Entomoloiat and Chief of Bureau.



PAPERS ON INSECTS AFFECTING VEGETABLES.


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BUREAU OF ENTOMOLOGY.

L. 0. HOWARD, Entomologist and Chief of Bureau. Il
C. L. MARLATTr, Entomnologist and Acting Chief in Absence of Chief.
R. S. CLIFTON, Executive Assistant.. :!
W. F. TASTET, Chief Clerk.

F. H. CHITTENDEN, in charge of truck crop and stored product insect investigation. ii
A. D. HOPKINS, in charge of forest insect investigations. Ji
W. D. HUNTER, in charge of southern field crop insect investigations. M
F. M. WEBSTER, in charge of cereal and forage insect investigations. 'M
A. L. QUAINTANCE, in charge of deciduous fruit insect investigations. :;
E. F. PHMLLIPS, in charge of bee culture.
D. M. ROGERS, in charge of preventing spread of moths, field work. "
ROLLA P. CURRIE, in charge of editorial work.
MABEL COALCORD, in charge of library.

TRUCK CROP AND STORED PRODUCT INSECT INVESTIGATIONS. i

F. H. CHITTENDEN, in charge.

H. M. RUSSELL, C. H. POPENOE, WM. B. PARKER, H. 0. MARSH, THios. H. JoHN2I%
M. M. HIGH, FRED A. JOHNSTON, entomological assistants.
I. 3. CONDIT, collaborator in California.
P. T. COLE, collaborator in tidewater Virginia. :
W. N. ORD, collaborator in Oregon. i!
MARION T. VAN HORN, preparator.











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CONTENTS.


Page.
Injurious occurrences and notes on habits................................... 17
Descriptive.............................................................. ... 19
The m oth .............................................................. 19
The egg-............................................................... 20
The larva-.............................................................. 20
The pupa............................................................... 20
Distribution.......................................................... .... 21
Historical and biological notes............................................... 21
Natural enemies-............................................................ 21
Associated insects-......................................................... 21
Rem edies ................................................................. 22
Paris green-............................................................ 22
"Dragging the log" ..................................................... 22





ILLUSTRATION.


FIG. 3. The southern beet webworm (Pachyzancla bipunctalis): Moth, larva,
pupa, details................................................... 19
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T. C. & S. P. I. I., November 11, 1911.


PAPERS ON INSECTS AFFECTING VEGETABLES.


THE SOUTHERN BEET WEBWORM.
(Pachyzancla bipunctalis Fab.)
By F. H. CHrTTENDEN, Sc. D.,
In Charge of Truck Crop and Stored Product Insect Investigations.
INJURIOUS OCCURRENCES AND NOTES ON HABITS.
On September 24, 1906, the Bureau of Entomology obtained from
Mr. F. W. Roeding, Wichita Falls, Tex., the larvae, pupae, and adults
of the pyralid moth Pachyzancla bipuntalis Fab., which had been
found operating on foliage of table beets in that vicinity. One larva
transformed to pupa on September 25, and the adult issued October
3, the pupal period thus having occupied eight days in an average tem-
perature of about 70 F. From this lot images continued to issue
until October 2, and a larva matured October 10 which would have
produced an imago about October 30.
During October, 1907, Mr. H. M. Russell observed larvae at Dade
City, Fla., on beet tops from 6 to 8 inches high, "webbing up" the
leaves with the edges of the leaves folded together or joining two or
more leaves to make a nest in which to hide. From this conceal-
ment they emerge and eat the leaf cells composing it, usually
leaving the leaf skeletonized or very thin. In these nest-forming
and leaf-eating habits the insect resembles the related Pyraustidae.
Mr. E. B. Embry, located at Dade City, Fla., stated that the larvae
of this species had injured the foliage of small beets so badly as to
reduce his crop about 50 per cent. As late in the season as November
29, the webworm larve were found in another locality at Dade City,
some of which showed parasitism. In January, 1909, larvae were
observed attacking beets at Boynton, Fla., and in March, beets at
Miami, Fla.
From webworm material obtained October 18, one pupated October
23, and the moth issued November 8. Another larva pupated
November 6 and the adult issued on November 21, thus indicating a
pupal period covering from 15 to 16 days, in the latitude of Washing-
ton, D. C. In another case the pupal stage lasted from December 31
to January 22, or a total period of 23 days. The temperature at
Washington was moderately cold.


U. 1. D. A., B. E. Bul. 109, Part II.





PAPERS ON INSECTS AFFECTING VEGETABLES.


This species was observed in 1908, by Mr. D. K. McMillan, at
Brownsville, Tex., working in colonies on the foliage of pigweed.
(Amaranthus retroflexus), and on spiny amaranth (A. spinosus), t
larvte webbing and folding the foliage in the previously described
manner. The colonies in question came under observation on Apri|i
30, May 14, June 15, and November 5, 1908. Mr. McMillan al
observed the larvae in large numbers during the spring of that yeart,.j
working on "spinach" in the Rio Grande Valley and on beet foliage i|,
at Brownsville.
On May 28, 1909, Messrs. McMillan and H. 0. Marsh observed thesn:;ii..|:
larvae at Brownsville, Tex., embedded in the leaves of Amaranthvws .,:|
retroflexus. The larvae were not in abundance at that time, doubtless
owing to the extensive parasitism in May and June of the preceding i|
year (1908). This was the first observed appearance of the insect ".li
that year. ,i
During the same year this species twice came under the observers.
tion of Mr. H. M. Russell, in the first instance at Boynton, Fla., on ,ii
January 27, 1909, when the larvae were found in great abundance on
the foliage of table beets. They had nearly stripped an early plant- I
ing and were also abundant on a later planting. In many cases the
larve were present on the underside of the leaves and had drawn the.,
leaf into a fold, inside ot which they were concealed. In other cases
the larvae were concealed by the folding up of the leaf from the edge, ::
while in further instances two beet leaves were fastened together in
such a manner that the larvae were concealed between them. In
feeding, the leaf substance is usually entirely eaten through to the
surface, the leaf skeleton alone being left. The larva void a very
soft excrement which produces a filthy condition of the leaves, :
Later on, March 3, the larvae were found by Mr. Russell in fair abund-
ance on beet tops at Cutler, Fla., and still later at Miami, Fla., on
Anwranthus retroflexus. i
Beginning with March, 1909, parasitic cocoons were seen on the:ii
leaves of beets, and early parasitism was indicated by the presence o
of parasitic cocoons on other food plants. Amaranth is abundant '
along the edges of many fields in southern Florida, and it is impossible I
to destroy it to a very great extent, as it grows luxuriantly on hun.I
dreds of acres of unclaimed lands. It costs from $15 to $75 as |
acre to clear hammock for planting. Perhaps, therefore, it is just 40,|
well to allow the amaranth to remain and to spray the weeds as s 1
means of keeping this pest in check. There is little doubt that unl[e9ion:C,
the parasites continue their good work the species is likely to cause
serious outbreak at almost any time in the future. iiii
Of one lot of material received at Washington, D. C., the larvili
of which were nearly mature, it was noticed that they began to "spit
up" preparatory to pupation on May 7; the following day some


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THE SOUTHERN BEET WEBWORM.


S the larvawe had pupated and by May 20 the adults had commenced
to issue, thus giving a total period for the pupal stage of about 12
days. The moths were placed in a large cage with a growing beet
and at the end of the week all had died.
In other sending of material the moths were observed to issue on
May 25, June 3, and July 9.
The length of the egg stage was not ascertained, but it may be
safely stated to be approximately 6 or 7 days, in moderate or warm
weather. From eggs laid on June 5 and 6 the adults developed July
3, giving a total life cycle of 28 days, or 4 weeks, in hot weather,
which will be about the minimum for the species. Assuming that






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FPG. 3.-Southern beet webworm (Pachyzancla bipunctalis): a, Moth; b, larva; c, lateral view of first
proleg and abdominal segment of larva; d, pupa, with cremaster showing location of hooks at right.
a, b, d, About three times natural size. (Original.)
from 5 to 7 days is occupied by the egg stage, and approximately
the same number of days for the pupal period in hot weather, the
larval period would be approximately from 14 to 18 days. At least
four generations are indicated for this species, and it is possible that
there are more, but there are no positive data on record on this point.
DESCRIPTIVE.

The moth.-The moth in color varies from buff to very pale yellow-
ish gray. The wings are slender and the antennae long. In the pale
forms the wings are nearly transparent, and the surface is rather
S iridescent purplish. The wing pattern of the pale individuals is faint,
k much more so than the illustration (fig. 3, a) would appear to indicate,
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PAPERS ON INSECTS AFFECTING VEGETABLES.


but is a little more definite in the dark forms. Near the a "flk|..
margin of the forewings there are three rather conspicuous
dots, one near the middle and one each side. The underside of
wings is paler and somewhat similar to the upper. The eyes are flH
brown, nearly black. The abdomen is darker than the wings, "
there are two black spots on the anterior' margin of the third abdo'1f0
segment. The legs are long and slender. The total length of t
body is less than one-half inch (12 mm.) and the wing expeas MO
about 1 inch (22 to 26 mm.). :
The egg.-The egg is of irregular, short, oval outline, and cosidwrt
ably flattened upon the surface on which it is deposited. The daM
is pale yellowish, which looks green, owing to its semitransparence, :
permitting the color of the leaf to show through. The surface is'*
finely reticulated, and under a high-power microscope is seen to bet***
composed of minute, very irregular, moderately depressed areas,;
chiefly hexagonal and pentagonal in outline. The surface is rather '
strongly iridescent and glistens, presenting the appearance of a fishI
scale in miniature. Length, 0.6 mm.; width, 0.45 mm.
Eggs obtained in confinement, May 26, were deposited singly on i
the underside of beet leaves. Mr. Marsh also observed the eggs on i
the underside of amaranth leaves at Brownsville, Tex., June 22, 1909.0;
The larva.-The larva (fig. 3, b, c) is slender, cylindrical, and in the
arrangement of the piliferous tubercles resembles Lozostege simils ...
Guen. and L. obliteralis Walk. The tubercles are not conspicuous in
living specimens, but become prominent in preserved material. The
color of the larva is dark, dirty green, with dark, mottled brown-and-
black, or nearly black, head and thoracic plate, the latter widely sepa
rated at the middle. The dorsal piliferous tubercles are large and,
black, the two pairs being closely jointed. The remaining tubercles aret
large and infuscated, the dorsal ones transverse and arranged in two A
pairs, one pair on each segment. The tubercles of the last segment :
form a central plate, with a lateral one each side, in front of the largw
anal plate. When boiled for preservation the larva becomes perfectly
white, bringing into prominence the rings of tubercles which com ..
pletely encircle each segment. The length of the larva when fult
grown is about three-fourths of an inch (19-20 mm.), and the width:.'
3 to of an inch (2.5-3 mm).
The pupa.-The pupa (fig. 3, d) is mahogany-brown, moderately
slender, with the anterior extremity rounded, and the posterior pro-: ?:!
longed into a bill-shaped cremaster, armed at the end with four veTy*,:'
fine hooks, one lateral and two apical pairs, their tips stroznly':.;3
recurved. The abdominal segments are without spines. The langtk
is about two-fifths of an inch (10 mm.).
The species is a pyralid and is placed in our lists next to LIxoos
It bears some resemblance to Loxostege similalis, but i consider
larger. 3


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20






THE SOUTHERN BEET WEBWORM.


DISTRIBUTION.

This is without doubt a species of tropical origin and inclined to be
cosmopolitan in any country suited to it climatologically. We have
in the National Museum collections material from Pernambuco, Bonito
Province, Brazil, as well as from Georgia, Texas, Florida, and the
District of Columbia. It is recorded also from the West Indies and
South Africa.
HISTORICAL AND BIOLOGICAL NOTES.

This beet webwormni was first described as "Phala'na 2-punctalis,"
in 1794.1 In the year 1880 the larva was observed feeding upon
cauliflower at Savannah, Ga., where it was stated to be very destruc-
tive. In consequence it was given the name of "Cauliflower botis." 2
It was also noticed that it fed on ragweed (Ambrosia), which is
probably the original food plant, cauliflower being an acquired one,
and perhaps not a food plant under normal conditions. The following
year it was again noticed at Savannah, Ga., on pigweed, the larvae
webbing the leaves together and destroying many plants. Nothing
further seems to have been recorded of its habits.
NATURAL ENEMIES.

Phorocera erecta Coq., a tachina fly, was reared from this species in
September, 1906. This parasite has been reared from the related
Loxostege similalis, at Victoria, Tex.
Amorphota sp. near orgyia', an ichneumonid parasite, was reared
January 15-29, 1908, from Pachyzancla bipunctalis, obtained from
Dade City, Fla., in October and December of the preceding year. A
single female before the writer measures 8 mm. in length and is
opaque black, with castaneous abdomen and middle and posterior
legs. The fore legs, and the tibiae and tarsi on the middle pair of
legs are light yellow, as is also the first joint of the antenna, the
remainder of the antenna being black.
Bracon sp., a small blackish species of this genus,4 was reared from
this host at Brownsville, Tex., November 21, 1908.
ASSOCIATED INSECTS.

In addition to the parasitic natural enemies of this species which
have been mentioned, some interesting species have been reared.
Prominent among these is a moth of the same family and with some-
what similar habits, known as the Hawaiian beet webworm 5 (Hy-
menia [Zinckenia]fascialis Cram.). It was reared by MAir. H. M. Rus-
t Fabricius, RFtomologia Systematica, vol. 3, pt. 2, p. 232, 1794.
2 Botis repetitalis Grote, n. sp., Comstock, J. H.-Rept. U. S. Dept. Agr. for 1880, p. 270, 1881.
S Chttn. No. 3030.
4 Chttn. No. 1064".
Bul. 109, Part I, Bur. Ent., U.S. Dept. Agr., 1911.






PAPERS ON INSECTS AFFECTING VEGETABLES.


sell, at Cutler, Fla., March 23-29, 1909. It is interesting to
that Mr. H. 0. Marsh has found this species very destructive to
beets in Hawaii, and has made a special study of it for the ButM6.a
of Entomology.
An agromyzid fly was reared February 17, 1909, with this b
webworm from material received from Mr. H. M. Russell onbe
and Amaranthus collected at Boynton, Fla.
Pegomnya ruficeps Stein, an anthomyiid fly, was reared under prn&J..
tically the same conditions as the moth Hymenia fascialis Cram.",
above mentioned. :
REMEDIES.
The remedies that have been advised for use against the gardu.C:"
webworm (Loxostege similalis Guen.) should be found about equanll.y
effective against the present species. In any case 'their use is advised:.,11
until more is learned of the habits of the southern beet webwoa^^ j
These remedies are given below. i
Paris green.-Paris green is applied at the rate of 1 pound to from..*;n
75 to 100 gallons of water, or dry, distributed with a powder gun, miI
practiced in the South. The latter method, however, is inferior to I
spraying. Since the two species share common natural food plazits&:||
(Amaranthus), the usual care should be exercised to avoid planting l
beets in fields which have grown up in this weed until after thorough,'*:
fall or spring plowing.
The experience which Mr. H. 0. Marsh has had with the related
Hawaiian webworm conclusively shows the value of Paris green. He
states, in brief, that a spray of Paris green at the rate of 2 pounds of
the arsenical and whale-oil soap, 8 pounds in 100 gallons of water,
proved absolutely effective and did no injury to the plants on which
it was applied. The spray was applied to the underside of beetiiii
leaves.1 More complete information in regard to this is given in '
Part I of the present bulletin. a
It should be added that a mixture composed of nicotine sulphate,'
1 fluid ounce, with whale-oil soap, 4 ounces, in 4 gallons of water, :l
was used by Mr. Marsh against a number of noxious lepidopterous :
larvae, and although this formula was not tested on the Hawaiian ::'
beet webworm, he believes that it would prove entirely effective. II
Dragging the log.-In the case of a bad attack of the garden web- .4
worm in Oklahoma in 1903, a satisfactory barrier to migration was :
employed, consisting of a dust furrow in which a log was dragged. i
This might be used in case the webworm under discussion should,*|
occur in great numbers before its presence is discovered-something:`::
that is likely to happen, as in the case of species of related habits.
SFor some reason arsenate of lead applied to both sides of Amaranthus leavewas found aaltiave
no explanation could be made of this, but the chemical was probably not pure.
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