30 
THE WHEAT-STRAW WORM. 
(Isosoma tritici, Riley.) 
Order, Hymenoptera. Family, CHALCIDIDE. 
[Plate II, Figs. 3 and 4.] 
This insect, although first noticed less than four years ago, has 
now become a decidedly injurious enemy to wheat in Southern. Illi- 
nois, doubtless diminishing the yield of the most important crop of 
this region by many thousands of dollars annually. There is, more- 
over, no reason to infer that it has yet reached its limit, although 
it has already become, locally, at least as expensive a guest of the 
wheat farmer as the Hessian fly. 
On the other hand, these injuries and losses, serious as they are, 
may certainly be almost perfectly controlled and prevented by sim- 
ple, easy, and inexpensive measures, which each may take individu- 
ally, without depending on his neighbors for cooperation, provided 
only that the characters and the life-history of these insects are 
understood. This is, in fact, one of those simple and satisfactory 
cases where a mere knowledge of the life history of the injurious 
insect is sufficient to suggest effective measures for its destruction, 
without awaiting the issue of tedious and often difficult and expen- 
sive experiment. 
These facts will certainly justify a full and careful discussion of | 
the wheat-straw worm, and make it especially important that a 
thorough knowledge of it be widely disseminated among those in- 
terested in wheat ‘culture in Southern Illinois. It is true that this 
species has already been treated at considerable length in the 
eleventh report of this office, in an article by Prof. G. H. French, 
but unfortunately at the time when this report was written, the 
wheat-straw worm had not yet been distinguished from a very differ- 
ent species, which is probably one of its parasites; and, as a con- 
sequence of this confusion, several statements were made which 
involved not only technical, but practical errors. It is now apparent 
that this species was there given the wrong generic name, that the 
adult or imago described did not belong to the same species as the 
larva, that the life history of the two species was mingled, and that 
important but mistaken practical inferences were drawn from an in- 
correct supposition that most of the adults were winged. It seems 
indispensable, therefore, that the matter should be cleared up, and 
economic recommendations made, based on a complete acquaint- 
ance with the habits and life history of the species; but it is pro- 
per that, in presenting this account, I should disclaim all credit for 
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