250 Insects Injurious to Vegetation. [Oct,, 



the acuteness of discrimination possessed by that eminent natural- 

 ist, we think must dispel the last lingering doubt as to the iden- 

 tity of the American and European insects. As will fully appear 

 in a subsequent part of this paper, the Hessian fly presents this 

 singular anomaly, that its pupae is coarctate, or enclosed in a case 

 like those of the other families of dipterous insects, but unlike 

 all the pupae of the Cecidomyians and other Tipulidae that have 

 been hitherto observed! The very fact, therefore, which leads 

 Mr. Westwood to suspect the European insect is not a Cecidom- 

 yia, all but demonstrates that it is the Hessian fly! 



Its Introduction into America. 



The existence of the Hessian fly in Europe being premised, so 

 many circumstances conspire to render it probable that it was in- 

 troduced into this country in the mode originally supposed, that 

 scarcely a doubt can now be entertained upon this point. 



When the habits and transformations of the insect itself are 

 considered, it will be perceived that these interpose great obsta- 

 cles to its being transported across the Atlantic, at a period when 

 two months or more were required for the voyage. Its passing 

 through two generations in a year, make its continuance in any 

 one stage of its existence comparatively brief The first of these 

 generations occupies about seven months, from October to April 

 inclusive. This generation is nurtured at the roots of the young 

 plants, and there is no probability that any of these plants would 

 be taken up, so that the insect could thus be conveyed away. 

 The second generation is nurtured in the lower joints of the straw. 

 The worm attains maturity in May, becomes a dormant " flax 

 seed " in June, continues in this state till August, when the fly 

 comes out to deposit its eggs in September. Though most of 

 these flax seeds remain in the stubble when the q-rain is harvested, 

 numbers of them are so high in the straw, as to be gathered with 

 it. But they are so firmly imbedded in the straw, and enveloped 

 within the sheathing base of the leaf, that it must be rare that 

 any of them are detached by the flail in threshing, so as to find 

 their way among the grain, and thus with it be carried to a dis- 



