44 
PARASITES. 
Surprisingly little of a definite and accurate character lias been 
published on the parasites of this interesting and important insect 
and nearly all the facts now current have been derived from almost 
the first competent observer of the fiy in America. The only species j 
carefully described is Semiotellus destructor, first noticed by Say. and I 
studied, as to its habits and life history, with some care by him. 
and especially by Prof. Herrick, of Yale College in 1838. One other 
parasite, Platygaster error, has been described by Fitch, but its life 
history has been only imperfectly worked out and inaccurately 
stated. A few other forms have been mentioned, without names or 
full descriptions, by Herrick, Fitch and Cook. 
The data herein presented are in themselves very incomplete, but 
are as full and definite as I have been able to make them, with 
two years study, in respect to the life histories of the parasitic 
species found to affect the Hessian fly in Illinois in any important 
way. 
The common Semiotellus destructor is here reclescribed in detail 
and descriptions are given of three new species bred from infested 
wheat, and mention is made of two others not fully studied,—and 
for all these species I have given full abstract of our breeding cage 
records. 
It is proper to say that, as my studies were made with principal 
reference to the life history of the Hessian fly itself, I was especially 
solicitous to depart as little as might be from the natural condi¬ 
tions of the species, and hence did not remove the flaxseeds from 
the straws, as would have been desirable for the breeding of the 
parasites only. From this it results that some of the parasitic 
species may have infested other wheat insects than the Hessian by, 
Indeed, as Eupelmus allyni appeared quite frequently in these breed¬ 
ing cages, and as this species has been supposed to be parasitic on the 
wheat straw worm only, it is not impossible that some of our straws 
were inhabited by this last species also, and that some of the new 
parasites herein mentioned belong to Isosoma.* 
Semiotellus destructor, Say. 
Order Hymenoptera. Family Chalcidid^. 
This is far the commonest of the parasites of the Hessian fiy in 
Illinois, 85 per cent, of those appearing in our breeding cages (ex¬ 
cluding Eupelmus) belonging to this species. It has been repeatedly 
described by Say, Fitch and Packard, but so imperfectly or inac¬ 
curately that I have not found it easy to identify the species posi¬ 
tively. Not doubting, however, that our most abundant form belongs 
here, I give a fresh description of both sexes, carefully drawn Iron 
alcoholic specimens. 
*Prof. Riley writes me that he has repeatedly bred Eupelmus allyni from the Hessian 
fly. 
