Apr. 15, 1925 
Larvae Resembling the Corn Borer 
785 
rates penitalis from nubilalis, as fol¬ 
lows: 
Epicranial puncture O a lying postero-dorsad of 
ocellus VI; mandible longer than broad; distal tooth 
concaved— P. penitalis. 
Epicranial puncture O a lying directly posterior to 
ocellus VI; mandible square, distal tooth pointed— 
P. nubilalis. 
(PI. 2, I, J.) 
PHLYCTAENIA RUBIGALIS GUENEE 
Scopula rubigalis Guen., 1854, Delt. et Pyr. 
(Bdv. et Guen., Hist. Nat. Ins. Lepidop.) 
8 : 398. 
Botys oblunalis Lederer, 1863, Wien. Ent. Mon- 
atschr. 7: 372, 469. 
Botys harveyana Grote, 1877, Canad. Ent. 9: 104. 
Phlyctaenia ferrugalis auct. (nec Hiibner). 
Pionea rubigalis Guen. Hampson, 1899, Proc. 
Zool. Soc. London, 1899: 242. 
Phlyctaenia rubigalis Guen., Chittenden, 1901, 
U. S. Dept. Agr., Div. Ent. Bui. 27: 7; Slinger- 
land, 1901, N. Y. Cornell Agr. Exp. Sta. Bui. 
190: 159; Busck and Heinrich, 1925, Jour. Agr. 
Research 29:140. 
Phlyctaenia, rubigalis Guen. (the green'' 
house leaf-tyer) is apparent^ the most 
widespread and troublesome insect 
pest with which greenhouse operators 
have to contend. It is especially 
troublesome where chrysanthemums 
are exclusively grown. In New Eng¬ 
land practically every greenhouse ex¬ 
amined in 1920-21 was severely in¬ 
fested by this insect. Although it is 
primarily a pest of chrysanthemums, 
it has also been found to attack rose, 
violet, snapdragon, and geranium. 
Davis (5, p. 100) found in Illinois that 
chrysanthemum and spearmint were 
particularly subject to attack. Infes¬ 
tations have also been found in celery, 
cabbage, beets, lettuce, cauliflower, and 
strawberry among garden crops. Many 
more plants, both ornamentals and 
vegetables, not mentioned here, doubt¬ 
less are fed upon by the larvae of this 
species. 
In 1921 the moths appeared in num¬ 
bers in chrysanthemum houses the 
first week in May. From this time 
until the blooms and plants were cut 
in October and November the insect 
bred continuously. During the months 
of July, August, and September it was 
possible, on examination of greenhouse 
chrysanthemums, to find the insect in 
all stages of development—eggs, larvae, 
pupae, and moths. It was practically 
impossible to follow the broods in the 
field on account of the overlapping of 
generations. 
After the blooms are marketed in 
October and November growers cut 
the old plants back severely, dumping 
or burning the tops out of doors. The 
old plants thus pruned soon give forth 
shoots which are used for the new 
crop of chrysanthemums the subse¬ 
quent season. This dumping or burn¬ 
ing of the tops reduces in a large meas¬ 
ure the infestation, since practically all 
the developing larvae and pupae are 
removed from the house. Moreover, 
the moths flying in the houses have no 
further place for oviposition, and since 
it requires a week to 10 days for the 
old plants to produce shoots the ma¬ 
jority of the insects die and the house 
is rid of the pest. In houses where a 
variety of ornamentals is grown the 
insect breeds continuously through the 
entire year; it is equally abundant in 
winter and summer. Davis (5) noted 
that the insect was rarely found in 
greenhouses during the winter months 
and attributed the fact to the cooler 
temperatures prevailing in houses in 
the winter. In the spring, greenhouses 
are apparently reinfested from moths 
emerging from the old chrysanthemum 
tops or litter out of doors, gaining entry 
through the ventilators. In midseason 
in 1921 it required 35 days under glass 
for the insect to complete its develop¬ 
ment from egg to adult. The larvae 
usually pupate in the webbed-up leaves. 
The larvae (pi. 1, F) for the most 
part are surface feeders—a few in¬ 
stances have been noted in market 
gardens and from specimens received 
at the Arlington laboratory of the 
entry of the larvae into the stems of 
celery—feeding on the under surfaces 
of the leaves of chrysanthemum and 
also webbing the leaves together with 
strands of silk, forming thereby an 
irregular fabrication in which they live. 
They have also been observed to feed 
on the leaf buds in the axils of the ex¬ 
panded leaves and on the flower buds, 
which on opening produce imperfect 
blooms. When the larvae are numerous 
this latter type of feeding greatly dis¬ 
counts the market value of the blooms 
but has no serious effect on the vitality 
of the plant. 
Full-grown larvae slightly resemble 
the European corn borer in a super¬ 
ficial way. The distribution of the 
setae on the body is almost identical in 
both species. Both are pyralids. The 
larvae measure when full grown 0.68 
inch in length. They are pale sage- 
green in color and strongly trans¬ 
lucent, so that portions of the trachea, 
particularly about the spiracles, may 
be seen through the cuticula in living 
specimens. Average specimens bear a 
dark green stripe on the median dorsal 
plane and two white broader stripes 
halfway between the former and the 
pleura. The head capsule is pale yel¬ 
low and mottled; the thoracic and anal 
shields are light yellow. The chitin- 
ized areas about the tubercles or 
