April, ’18] McCONNELL: A PARASITE OF THE HESSIAN FLY 171 
infested stems or stubbles with antennae bent forward and downward 
and kept in constant vibration. When a suitable location is found, 
the abdomen is contracted longitudinally, the tip bent downward and 
the ovipositor pushed into the stem. If no puparium is present, the 
ovipositor is promptly withdrawn, but when a host is found oviposition 
may require several minutes. They oviposit only during daylight, 
and preferably during bright weather. 
A female may lay as many as five eggs in a day, and probably more. 
She may rest from oviposition for a day or two at a time. Females 
have lived in cages and oviposited over a period of 3 to 24 days, and 
other females which never oviposited have lived as long. The maxi¬ 
mum number of stages reared from a single female was 39, but it is 
necessary to make allowance for considerable mortality, and it seems 
probable that a female ma}^ lay at least a hundred eggs. On the other 
hand, some females seem to be unable to oviposit. These are small 
individuals which for one reason or another have had an insufficient 
amount of food during the larval period. 
Unfertilized females are thelyotokous. Mr. P. R. Myers has reared 
this species through five successive parthenogenetic generations and 
the writer, starting with a different female, has carried them through 
six such generations without the appearance of a male in any case. 
The sixth of these generations appeared during the past summer, but 
the individuals were small in size and never oviposited. This was 
undoubtedly due to a scarcity of good host material upon which they 
could develop, and not to the lack of fertilization. 
The Egg 
The eggs (Fig. 8, 1) are deposited on the outside of the host larva or pupa inside the 
puparium, and cling lightly to the host. They are white in color. The chorion is 
thin and elastic, with a smooth and shining surface. They are ellipsoidal in form 
with a large pedicel at the cephalic pole and a slender flagellum at the caudal pole. 
They measure 0.374 mm. in length by 0.133 mm. in greatest width, taking the aver¬ 
age of five eggs. The pedicel is about half as long as the egg and is usually folded 
back along the side of the egg, its tip being recurved forward, but it may be bent 
and twisted in various ways. The flagellum at the posterior pole is about half as 
long as the pedicel and usually lies against the posterior surface of the egg. It is 
very slender and structureless, and, as Marchal (2) has suggested for Platygaster and 
related genera, it probably results from the degeneration of the follicular cells sur¬ 
rounding the posterior pole of the ovarian egg. 
During April and May in the laboratory the eggs hatched in about 
three days. In the process of hatching the larva breaks through the 
chorion near the base of the pedicel and slowly crawls out. 
The Larva 
The larva when first hatched is about 0.4 mm. long, slightly depressed, widest in 
the metathoracic region, and tapering to a rather acute abdomen. The head is com- 
