18940 



HESSIAN FLY 



were not merely varieties until this point was noticed by a 

 Dutch entomologist, Mr. Snellen. I shall be glad to refer 

 to this point, for it is important and was observed after our 

 chief manuals of Lepidoptera were published. 



On referring to your letter accompanying the Hessian fly 

 puparia, " flax-seeds," in which you notice some of them 

 being within the stalks, I remembered I had not precisely 

 replied to this part, so I do it now. I think this position, 

 though not characteristic, is not very uncommon, and is 

 caused by a weakness of the stem. I have from time to 



B+KO 



Natural size and magnified. 



i, Anchor-process of larva of Cecidomyia destructor; 2, of Cecidomyia 

 triiici magnified ; " flax-seeds," or puparia, in different stages of 

 development, natural size and magnified. 



FIG 15. HESSIAN FLY, CECIDOMYIA DESTRUCTOR. 



time found the stem cracked longitudinally and the " flax- 

 seed " partly slipped into the cavity. 



August 22, 1894. 



I have to-day had a request from Dr. Ritzema Bos for 

 some specimens of Hessian fly puparia /'// situ or otherwise. 

 If you could do it without inconvenience, could you oblige 

 me with some " flax-seeds " if you come on them at threshing 

 time ; and you will be good enough to let me have also a 

 few pieces of barley or wheat stem just three or four inches 

 long with the flax seed still adhering. 



