786 
Journal of Agricultural Research 
Vol. XXX, No. 8 
pinacula are pale (10, p. 142 ), indis¬ 
tinct, and sometimes wanting entirely. 
The chitinization of the pinacula forms 
the chief character whereby they can 
be readily separated from the larvae 
of the corn-borer group. 
Two near relatives have been reared 
at the Arlington laboratory: Phlyc- 
taenia tertialis Guen. from elderberry, 
in which it breeds and overwinters as 
a larva, and Phlyctaenia terrealis Tr. 
from carnations. The larva of the 
latter enters the stem of the carnation 
plant through the crown of terminal 
leaves. Its presence is readily detected 
by the wilting of this section of the 
plant which growers pinch off and un¬ 
fortunately throw in the walks of their 
greenhouses. The larvae soon desert 
these pinched-off parts and return to 
the living plants to reinfest them. 
This wilting bears much resemblance 
to the wilting in certain plants result¬ 
ing from the attack of the European 
corn borer, but the latter is not known 
at this time to infest carnation. 
DIATRAEA ZEACOLELLA DYAR 
Diatraea zeacolella Dyar, 1911, Ent. News 22: 
203; Barnes and McDunnough, 1917, Check 
List Lepidop. Bor. Amer. No. 5437. 
Previous to Dyar’s separation and 
description of Diatraea zeacolella (the 
larger cornstalk borer) in 1911 en¬ 
tomological writers on economic sub¬ 
jects referred to this insect as Diatraea 
saccharali.s Fab., believing the species 
injuring corn identical with the one 
doing damage to sugar cane. 
The larger cornstalk borer is pri¬ 
marily a southern insect. The records 
by various workers, especially Leiby 
(17, p. 10), show that it extends from 
Delaware to Florida, west to Louisiana, 
and possibly occurs in Kansas, Okla¬ 
homa, and Texas. It passes through 
two complete generations, one in the 
spring and early summer and the 
other in late summer and early fall. 
The overwintering larva pupates in 
the early spring. 
The principal food plant of the in¬ 
sect is the corn plant. Other food 
plants have been recorded as: Gama 
grass, sorghum (sorgo), sugar cane 
(Howard), probably Johnson grass, and 
Guinea corn (Ainsiie). 
On hatching from the eggs the larvae 
feed on the epidermis of the leaves of 
corn (17, p. 28), finally working their 
way into the unopened whorl of corn 
leaves which on expanding contain a 
rather uniformly sized series of holes 
running across the breadth of the leaf 
(19, p. 8). Another series of irregular 
perforations in the leaf may also be 
present when it fully expands, owing 
to the fact that the larvae feed within 
the bud in an irregular way, horizon¬ 
tally or upward, or downward. 
After feeding in either fashion for a 
time the larvae desert this part of 
the corn, migrating downward and 
reentering the plant generally between 
the first and second joints. Since the 
insect has two broods and the nature of 
the feeding for the two generations of 
larvae is closely parallel, much real 
injury is caused to growing corn, the 
growth of the plant being impaired and 
production being consequently dimin¬ 
ished. The larvae apparently never 
attack the grain on the ear as do those 
of the European corn borer. “The 
larger cornstalk borer habitually passes 
the winter in the taproot of the corn 
plant, whereas nubilalis may be found 
at any point in the stalk and in the 
ear” (Caffrey). 
Although the larger cornstalk borer 
possesses many structural characters 
common to the European corn borer, 
the two larvae differ quite radically in 
appearance. The larvae of Diatraea 
zeacolella are of two types, a summer 
and a winter form. The essential 
difference between the two types con¬ 
sists in the pigmentation of the pinac¬ 
ula. In the summer form they are 
orown to black, well defined, in strong 
contrast to the white body and honev- 
yellow head. In the winter form these 
areas have all faded out, are pale, in¬ 
distinct and seem to fuse with the 
whiteness of the body. The larvae 
average 24.9 mm., or almost an inch in 
length. They are, therefore, slightly 
longer than nubilalis, and more robust. 
The supracoxal pinaculum on the 
mesothorax in Diatraea bears two 
setae, No. VI 7 (pi. 2, C); in nubilalis 
this same area is unisetose, seta VI 
(pi- 2, A) (15, pi. 4, fig. 1). 
7 Larval chaetotaxy is a difficult study. It is particularly difficult to trace setal homologies. The writer 
makes no pretense of being well informed on the subject. The Roman numerals employed in designating 
setae follow the system of Dyar, who did the pioneer work in America on this subject. Heinrich’s papers 
have been freely consulted and studied. Fracker {10) has instituted a nomenclature of Greek letters, be¬ 
lieving that by its utilization one can more readily grasp the homologies of setae. It seems that Fracker 
established his homologies by plotting one segment above the other. He failed, however, to take note of 
the fact that the hairs occur on definite body areas and that their changes in position are caused by modi¬ 
fications of the areas themselves. It has been pointed out clearly by Heinrich that when hairs are absent, 
as frequently happens on the ninth abdominal segment, it is necessary to trace the folds to determine what 
body areas have been reduced or crowded aside before one can decide what particular seta is missing. 
Fracker did not do this and, therefore, frequently has given the wrong designation to his seta. Fracker’s 
system apparently would have been, in many ways, an improvement over the Roman method if he had 
correctly worked out the homologies between the segments. 
