290 
Journal o f Agricultural Research 
Vol. XXIX, No. & 
fly puparia in the laboratory both at 
Hagerstown, Md., and Carlisle, Pa., 
yet in the course of the investigations 
it has been possible to secure only 13 
specimens of this species from material 
collected in the field. In view of the 
fact that so few specimens have been 
reared from material collected in the 
field, it would seem that this species is 
one of the rare and less important 
parasites of the Hessian flv. Adults 
have been reared from Hessian fly 
puparia, both of the fall and spring 
generations. The maximum percent¬ 
age of parasitism obtained from mate¬ 
rial of the spring generation was 0.85 
per cent, whereas in the material of 
the fall generation it was 1.5 per cent. 
EGG 
The egg (fig. 1, a) is translucent 
whitish in color. In shape it is rather 
ovate with the cephalic end larger and 
more obtuse than the caudal end. It 
is about two and one-half times as long 
as its greatest width. The ventral 
region is slightly concave and the dorsal 
region convex. The chorion is thin 
and elastic and is almost entirely 
densely spinose. There is a small 
circular area at the caudal end bare of 
spines. The spines are of uniform 
length everywhere except close to the 
periphery of the smooth area. Here 
they shorten declivitously. The length 
of the egg varies from 0.34 to 0.38 mm. 
and its greatest width varies from 0.14 
to 0.15 mm. The average measure¬ 
ment of 10 eggs was 0.36 mm. in 
length by 0.15 mm. in greatest width. 
incubation 
During the month of July when these 
experiments were conducted, the period 
of incubation varied, occupying from 
one and one-half to two days. In 
hatching, the young larva pushes its 
head against the ventral portion of the 
cephalic end of the egg, stretching the 
elastic chorion at this point into a 
blunt protuberance. After pushing 
against the chorion for some seconds 
the larva withdraws into its normal 
position. This process is repeated 
after short intervals for an hour or 
more before hatching actually occurs. 
During the effort of the larva to break 
through the chorion the posterior 
part of the shell is contracted irregu¬ 
larly by the forward movement of the 
larva, and the mandibles of the young 
larva can be observed opening and 
closing within. 
PRIMARY LARVA 
The newly hatched larva is about 
0.35 mm. long, or about the length of 
the egg itself. It is widest at the 
cephalic end but tapers gradually to a, 
rather acute point at the caudal end. 
There are rather prominent tubercles 
on each side of the anterior body seg¬ 
ments, each of which is surmounted by 
a coarse seta. The head bears a pair 
of antennae and some fine setae. 
The mouth, which is of a protruding 
suctorial form, is readily discernible. 
In its attack upon its host the young 
parasitic larva may attach itself to any 
part of the host’s body. 
MATURE LARVA 
The mature larva (fig. 1, b) varies 
from 1.5 mm. to 2 mm. in length and. 
frond 0.5 mm. to 0.6 mm. in width. 
The average length of 10 larvae was 
1.7 mm. and the average width was 
0.54 mm. It is of a typical chalcidoid 
form, somewhat spindle shaped, slightly 
curved, tapering to both extremities but 
more acutely toward the caudal than 
the cephalic end. It is white in color,, 
smooth, shining, and bare except for 
two rows of fine setae along the latero- 
dorsal area of the first 12 segments. 
These setae are arranged two to a seg¬ 
ment, one directly above the other. 
The body consists of 13 segments. The 
anal segment is divided into a dorsal 
and a ventral lobe, the dorsal lobe being 
margined posteriorly by a row of four 
setae. Spiracles are present on the 
mesothoracic, metathoracic, and the 
first seven abdominal segments. The 
head (fig. 1, c ) when viewed from the 
front is slightly concave giving it a. 
somewhat bilobed appearance. The 
antennae which are very short and pale 
brown in color are surmounted on a 
fleshy tubercle. The labrum is broadly 
ovate, slightly curved, and sparsely 
and finely setose. Two setae are dis¬ 
cernible on either side of the head, 
laterad of the mouth. The mandibles 
(fig. 1 , d) of the mature larva are about- 
0.03 mm. long. They are chitinous, 
light brown in color, simple in form and 
nearly straight. The superior margin 
of the mandible is slightly curved while 
the inferior margin is nearly straight. 
No other appendages of the mouth parts 
are discernible. 
The duration of the larval stage 
varies from 4 to 11 days. The average 
length of the larval period for 30 larvae 
was slightly more than 6 days. Table 
I shows the individual variation of the 
duration of the larval aftd other stages. 
