38 



abdomen is a little shorter, the whole insect being from .06 to .07 

 of an inch. The legs have all the femurs yellow, front tibise 

 yellow, middle and hind tibiffi fuscous, except at the apices, which 

 are yellow ; feet as in the females. 



3. Contributions to a Knowledge of the Life History and the 

 Parasites of the Hessian Fly. 



(Cecidomyia destructor, Say.) 



Order Diptera. Family Cecidomyidze. 



(Plates II and III.) 



Notwithstanding the enormous losses inflicted upon agriculture in 

 Illinois by this most destructive enemy of one of our important 

 staple crops, the details of its life history, upon which strictly 

 depend the value of measures for the prevention or control of the 

 injuries, have not been fully or accurately made out for any part 

 of the Mississippi Valley, the statements current on this subject 

 appearing in agricultural papers and in the writings of our local 

 entomologists, being mostly derived from the statements of Herrick, 

 Fitch, Harris, and other observers, who have studied the species in 

 the North Eastern States. 



It is, beyond question, chiefly to its parasitic enemies that we 

 owe such immunity from the Hessian fly as we now enjoy, these 

 clearly constituting the principal natural check upon its continued 

 existence in destructive abundance ; but our ignorance of its para- 

 sites is even greater than that of its life history, for almost noth- 

 ing definite has been learned concerning them since the observa- 

 tions of Herrick, of Connecticut, made in 1832 ; Certainly, therefore, 

 time and labor spent in acquiring more definite knowledge of the 

 details of the life history of the Hessian fly, and the number, 

 kinds, seasons and habits of the parasites will be well employed, 

 even if it should serve only to shake the confidence of our agricul- 

 tural community in such remedial measures as may have been 

 heretofore recommended. 



As soon after entering upon the duties of State Entomologist as 

 time and opportunity offered, I began observations upon this insect 

 with the view and hope of constructing a complete account of its 

 life history in the southern half of Illinois, — the only region lately 

 affected by it, since winter wheat culture, although now rising to 

 importance in the northern part of the State, has been too lately 

 revived there to expose the fields to danger from the Hessian fly. 

 The results here presented fall something short of a complete 

 account of the life history of this insect throughout the year, but 

 they nevertheless throw unexpected light upon the matter, and are 

 deemed worthy of report as a statement of the present condition of 

 the investigation. 



