36 
ed, however, are now much more distinctly marked than they pre~ 
viously were, the transverse lines being more deeply impressed, 
and the margins showing corresponding crenatures. No traces of 
the members of the future fly are yet discernible. The insect now 
undergoes no further change, for a period of five months or more.. 
Enyeloped in its flax seed like mantle, and reposing at the root 
of the now lifeless grain, it is buried beneath the snows of winter. 
Over one half of its entire term of life is therefore passed in this 
state. 
Error in previous accounts. This is the stage of this insect, 
which has been spoken of by all preceding writers as its pupa or 
chrysalis state. Upona close observation of the Cecidomyiu trit- 
ict, the writer succeeded in discovering that that species had, what 
some had conjectured, but none had actually observed, a regular 
pupa form, identical with that of other species of Cecidomyia, 
whose metamorphoses had been fully described. It hence appear- 
ed necessary to distinctly mark that long period of inactivity 
which intervenes in the wheat fly, after the larva has completed 
its growth, and before it enters its pupa state; it was therefore, 
during this state of its life denominated a dormant larva, in my 
essay upon that species. It occurred to me whilst writing out 
that essay, that the dormant larva state of the wheat fly, was ex- 
actly analagous to the flax seed state of the Hessian fly, and in a 
note, my suspicions were expressed that the real pupa of the Hes- 
sian fly had never been detected. The ample opportunities which 
I have since enjoyed for investigating this species, have enakled 
me fully to trace out this point in its transformations, and to show 
that it is not till near the close of its flax-seed period of existence 
that the Hessian fly puts on its pupa form. In penning the note 
just alluded to, I had overlooked a passage in Mr. Herrick’s last 
paper, from which it is obvious that he has seen the real pupa of 
the Hessian fly, although he still speaks of its pupa state as com- 
mencing when the worm becomes a flax seed. Inaccuracies of 
this kind, which to the general reader appear so trivial as scarcely 
to require correcting, are liable to lead to important errors. Of 
this, we have a striking illustration in this very instance. Mr, 
