te 
The Hessian Fly, and its Parasites. 157 
The pupx, which became such in and about June, evolve the 
perfect insect, partly during the next autumn, and partly during 
the year succeeding. 
Parasites.—There are in this region, four principal parasites 
of the Hessian fly, one of which attacks the eggs, and the other 
three the pup. They are all minute Hymenoptera. 
1. The egg-parasite, is a species of Platygaster, Latr., and 
may prove to be identical with some one of the hundred species 
of this genus which are described. (Entom. Mag. Lond. iii, 217. 
Cont: Macl. Lyc. i, 81.) The insect is abundant in the autumn. 
I first saw it Sept. 23, 1833, in the act of depositing its eggs in 
the eggs of the Hessian fly. From subsequent observations it 
appears that four or five eggs are laid in a single egg of the Hes- 
sian fly. The latter egg hatches, and the animal advances to the 
pupa state as usual, but from the puparium no Hessian fly ever 
comes forth. ‘This parasite forms within the puparium, a silky 
cocoon of a brownish color. 
2. This is the chief parasite of the pupa. It is described by 
Mr. Say, (Jour. Acad. Nat. Sci. Phil. i, 47,) as the Ceraphron 
Destructor. It appears to me not to belong to the genus Cera- 
phron, (Latr.) but to fall within the genus E’urytoma, of Illiger. 
It pierces the sheath of the stalk, (making a hole too small to be 
detected by a powerful microscope,) and deposits an egg in the — 
pupa within. This is done chiefly in June. The perfect insect 
is evolved in the summer and autumn succeeding, eating its way 
through the puparium and the sheath of the leaf. An insect (of 
which I have seen females only) very similar to the Eurytoma 
Destructor, but with mere rudiments of wings, is sometimes 
evolved from the pupee of the Hessian fly. Iam in doubt whether 
it should be considered a distinct species or only a variety. The 
winged individuals never throw off their wings. 
3. The next parasite of the pupa, is an insect of the tribe 
Chaleidie, (Latr. in Cuv. Régne An.) whose genus I have not 
determined. Its habits are like those of No. 2, but it is evolved 
ater. Apterous females of this species are also found. 
4. Another parasite of the pupa is an insect of the tribe Ox- 
yuri, (Latr. in Cuv.) whose genus I have not determined. Tn 
habits it agrees with Nos. 2 and 3, but it is evolved still later in 
the year. All of these parasites are likewise evolved in the 
Spring, from Hessian fly pupae of the summer previous. 
