8 
Mr. Westwood, in a note appended to this account, says, it is 
perhaps questionable whether the species, of which the above de- 
tails are given by M. Kollar, is identical with Say’s Cectdomyia 
destructor. He even intimates a doubt whether the European 
species is a Cecidomyia, for, from all that had been observed, this 
genus in its pup state, is naked, like the other Tipulids, and 
not enclosed in a case. Having himself received specimens from 
Dr. Hammerschmidt of Vienna, and still in the straw near the 
roots, he found the insect “enclosed in a leathery case,” on open- 
ing which, he discovered the /arva shrivelled up and dead. Now 
this nice point, so particularly noted, and so strikingly showing 
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 pupe is coaretate, or enclosed in a case 
like those of the other families of dipterous insects, but unlike 
all the pup of the Cecidomyians and other Tipulide 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. 
