38 
Westwood, on opening the flax seeds contained in the wheat straw 
from Germany, came upon “the larva,” where, according to all 
the accounts of the Hessian fly he ought to have found the pupa; 
he therefore at once draws the important inference, that the Ger- 
man insect cannot be the Hessian fly of America. Indeed it is 
surprising, that so plain a fact as-this, that it is a worm and not 
a pupa which is enveloped in the flax seed case of our insect, has 
been so wholly overlooked by every one who has hitherto written 
upon this subject. 
Tue Pura. When formed.—On the access of the first warm 
days of spring, as soon as the weather becomes sufficiently genial 
for some of our earliest plants to put forth their blossoms, the 
larva of the Hessian fly is rapidly stimulated to maturity. The 
present year, so early as the 21st of April, most of the insects 
were found to have taken on their pupa form. As this season 
was more forward than usual, this may prove to be an earlier 
date than is common for this occurrence; a more accurate criterion 
by which to indicate it definitely, is no doubt by a reference to 
the progress which vegetation has made at this time. We may 
therefore state, that in all parts of our country, the Hessian fly 
will probably be found in its fully formed pupa state, about a 
week after the liverwort, (Hepatica triloba,) the trailing arbutus 
(Epigea repens), and the red or swamp maple (Acer rubrum,) 
first appear in bloom, and simultaneously with the flowering of 
the dry strawberry (Comaropsis fragarioides), the common five- 
finger (Potentilla canadensis), the hill-side violet (Viola ovata), 
&c. It continues in this state about ten or twelve days, and then 
sends out the winged fly. 
Its characters. — The flax seed shell has now become quite 
brittle, breaking asunder transversely if rudely handled, and one 
of its ends slipping off from the inclosed pupa like a thimble 
from the end of the finger. On removing the pupa (fig. 7) from 
its case, it is found to be 0.13 long by 0.05 broad, of an oval 
form, with rounded ends, and having its limbs and body enveloped 
in separate membranes. The thoracic portion is slightly narrower 
than the abdominal. The wings do not quite attain the middle 
