804 
ANNUAL REPORT OF • NEW YORK 
MIDGE. THE PUPA. 
hinge to hold this lid to the cocoon, tho same as we see in th 
cocoons of multitudes of other insects. 
From the analogy furnished by other species of Cecidoinyh 
we infer that the larva of tho wheat midge will remain in iti 
cocoon through the winter and till the following May, when i 
will assume its pupa form. And in June, when ready to becom< 
a fly, this pupa will crowd open the. little lid above mentioned 
from the end of the cocoon, and work itself up nearly out of tin 
ground, when its skin will part asunder on the anterior end o 
its back and the fly will withdraw itself from it. 
Kept in vials in a warm room, I doubt not my cocoons wil] 
give out the flies much earlier than June, probably before the 
close of winter. And though the flies naturally come abroad 
only in June and July, with the knowledge I have now obtained, 
I am perfectly confident I can with the utmost facility so manage 
the larvm and cocoons as to produce the flies in every month oi 
the year. 
I must not leave this subject without describing the manner 
in which the insects of this genus Cecidomyia effect the change 
from their larva to their pupa form, as this is a point which has 
occupied much of my attention since I first began to investigate 
these insects, and on which important light has recently been 
obtained. 
As has already been mentioned, some larv® of the wheat 
midge found in March were placed in a vial of earth and in June 
the flics therefrom were found in this vial, and also the pup® 
skins from which these flies had hatched, but on a most careful 
search no traces of the cast skins of the larv® could be dis¬ 
covered; wherefore it appeared that the larv® must have 
changed to pup® without throwing off their skins. And this 
view that these insects do not cast olf a skin in becoming pup® 
was strongly corroborated by the Willow gall midge, to which 
allusion has already been repeatedly made. This is a large ro¬ 
bust species, double the size of the wheat midge and therefore 
of much easier examination. It forms a gall the size of a bird’s 
egg on or near the ends of willow twigs, through the middle of 
which gall is a cylindrical cell as large as the cavity in a rye 
stiaw, in which cell the larva resides, and when done feeding 
it weaves a thin partition across its cell whereby it incloses 
itself in its lower end and there takes on its pupa form. It 
