43 



Calendar — Continued. 



Although on a subject as difficult and important as that of the 

 midsummer history of the Hessian fly it is probably best to await 

 additional data before attempting to establish a final conclusion, it 

 must be admitted that the facts above stated strongly suggest the 

 hypothesis of a normal completion, before harvest, of the transfor- 

 mations of a considerable part of the destructive spring brood of 

 the larvae. 



It is with a sense of disappointment that I make this statement, 

 as this condition of things greatly diminishes the value of mid- 

 summer measures for the protection of our wheat fields, if it does 

 not indeed render them almost wholly useless. While undoubtedly 

 the burning of the stubble in the summer and other measures of 

 the sort must destroy a considerable number of larvse and pupae, it 

 seems possible that enough adult flies will have escaped before har- 

 vest to continue the species in scarcely diminished numbers. 



It may be objected that the earliest imagos that escape from the 

 spring brood of larvae may immediately lay eggs, and thus give 

 origin to an intercalated brood of larvae which form flaxseeds before 

 harvest, — perhaps in immature and stunted plants ; but it was to 

 this point above all others that our attention was especially given 

 this year; plants of all ages, from infested fields, being examined 

 by hundreds at a time, with almost microscopic thoroughness and 

 care with the express purpose (and I may add the lively hope) of 

 discovering such young larvae. The results of all this labor were, 

 however, absolutely negative. Not a single larva was found which 

 it seemed at all possible to suppose could have descended from 

 flies of later origin than those escaping from the flaxseeds which 

 had spent the winter in the fields. 



