June 15, 1921 
Life-History Studies of Three Jointworm Parasites 409 
of D. flavicoxus, though some specimens reared have much lighter-colored 
coxae than those of the average D. aureoviridis. 
HOSTS 
This species apparently prefers Harniolita tritici and H. vaginicola 
Doane, and the writers have reared it in cell slides on H. elymicola Phil¬ 
lips and Emery and H. grandis Riley. It probably will parasitize any 
of the gall-forming species of Harmolita, though the writers have reared 
it only from field collections of H. tritici f H. vaginicola, H. grandis, H. 
atlantica Phillips and Emery, and H. secalis Fitch. It breeds freely upon 
the larvae of Eurytoma spp. in the field and in breeding cages, and upon 
one occasion an egg was deposited in a Harmolita cell upon a pupa of 
Ditropinotus aureoviridis. It undoubtedly breeds upon Homoporus chal- 
cidiphagus also, though it plays the role of secondary parasite only when 
the individuals of Harmolita are very highly parasitized. 
EGG 
The eggs (PI. 75, A; 77, B) are deposited in the gall-like cells of 
Harmolita tritici external to the host larva. They are not always placed 
directly upon the host, but the small size of the cell of the jointworm 
requires that the egg be in close proximity to its host. The egg is grayish 
white in color and opaque. It is elongate, kidney-shaped, but asym¬ 
metrical. There is a nipple-like process at each end of the egg. The 
surface of the egg is covered uniformly with spicules with the exception 
of the nipple-like process at the posterior end. The average of four eggs 
measured 0.6772 mm. in length and 0.1583 mm. in greatest width. 
The period of incubation of 199 eggs in cell slides varied at different 
times during the breeding season from 1 to 5.5 days. The average time 
was 3 days. Low temperatures greatly retarded development. At the 
time the egg is ready to hatch, the mandibles of the young larva can be 
observed at the large end of the egg, where they move back and forth 
occasionally. Sometimes the whole outline of the head can be seen 
through the chorion just before the young larva cuts its way out with its 
mandibles. The round nipple-like process extended out beyond the 
larva's head makes it look as though it were wearing a dunce cap. The 
larva keeps pushing forward with its head against the flexible shell, at 
the same time slashing away with its mandibles until finally the shell is 
ruptured. The larva then forces its head through the aperture (PI. 
75, B) and begins feeding at once upon the host larva. Several hours are 
usually required for the larva to extricate itself from the eggshell. 
I/ARVA 
First instar (PI. 75, C).—The color of the first-instar larva is trans¬ 
lucent whitish. Just before the first molt the average length of three 
larvae was 0.9152 mm. and the average greatest width was 0.2060 mm. 
