40 
fledged and perfectly formed fly leaves its pupa skin and mounts 
into the air. 
Peculiarity in its metamorphoses.—It is sufficiently apparent 
from the account that has now been given, that the Hessian fly 
differs notably from all its congeners in one important point in its 
transformations. From all the observations that have been hither- 
to made, the cecidomyians correspond with the other tipulides in 
this prominent particular—that their pupe are naked. Other 
species, at least many of them, after completing their growth, 
cleave from their skins in the same manner that the Hessian fly 
does, but when the separation is formed, the inclosed worm inva- 
riably crawls from and forsakes its larva case. It is thus, even, 
contrary to what has been hitherto supposed, with the C. tritici. 
Since my essay upon that species was published, I have clearly 
ascertained that the mature or dormant larva does cast its skin. 
So far as I am aware, moreover, the cast skins in the several spe- 
cies are translucent, and of a membranous texture. In the Hes- 
sian fly, however, it becomes opake, changes its color, and is of a 
firm or coriaceous texture. The inclosed worm, also, does not 
leave it, but remaining, eventually changes within it to a pupa, 
the same case thus forming its puparium. Its metamorphosis thus 
approximates it to the Muscide or true flies, the Stratiomide or 
soldier-flies, &c. and its pupa, in technical language is “ coarctate” 
and not “incomplete” like the pupe of the other cecidomyians. 
Should usage therefore settle down upon the name midge as dis- 
tinctive of the minute tipulides, there will still be a marked pro- 
priety in continuing to this species its old name, Hessian fly.* 
*I doubt, however, whether the Hessian fly will continue to be the sole 
member of this genus having a coarctate pupa. Quite recently a species has 
occurred to my notice, analagous to the Hessian fly flax seed in every point 
that I have been able to detect, except that its Jarva case is of a pale brown 
color, untinged with rufous or castaneous. It infests the Agrostis lateriflo- 
ra?, numbers dwelling together in an imbricated gall, somewhat resembling 
the fertile aments of the hop, though larger, and connected with the main 
stalk by a short pedicel which is inserted into one of the lowest joints of the 
culm. From the coriaceous texture of the Jarva case, I suspect the inclosed 
worm will not Jeave it, until transformed to a pupa and upon the point of 
evolving the perfect fly. 
