268 Q.UARTERLY JOURNAL. 



through the horn-like summit of the gall, and almost entirely ouft 

 of the cleft orifice at its apex. Thus exposed to the air, its super- 

 abundant fluids rapidly evaporate ; the parts within the outer filift 

 which envelops its body, contract and become more firm, and the 

 fly gradually withdraws itself from the pupa skin, like a hand 

 drawn from a tight glove, and floats forth upon the wing, leaving 

 the blanched relicts of its pupa state adhering to the jagged teeth 

 at the apex of the gall. 



Enemies and Destroyers. PI. II. fig. 8. Upon this topic, my in- 

 vestigations are as yet too limited to give but a few facts, leaving 

 a more complete elucidation of it to a future occasion. 



A larva quite different from C. Salicis, is occasionally found 

 within the canal of these galls. It is of a dull pale greenish 

 brown color, rather larger than the Cecidomyia maggot ; its body 

 broadest anteriorly, moderately tapering towards the tail, and com- 

 posed of thirteen segments ; the head is darker and polished ; the 

 mandibles blackish, tinged with chestnut brown j each of the three 

 segments following,, bears a pair of legs terminated by black feet. 

 Viewed from above, it has a rugose or warty appearance, caused 

 by a row of slightly elevated and darker colored spots on each 

 side of the back, one being based upon the posterior edge of each 

 segment. Lower down, oh each side, is another similar row, the 

 spots being upon the anterior edge of each segment. This worm 

 is sometimes found in the upper part of the canal of the gall, 

 with the larva of C. Salicis occupying its usual place in the lower 

 part. But much oftener, at least in the latter part of winter, it is 

 found in the lower part of the canal, the larva of the C. Salicis 

 having disappeared. The presumption is hence strong, that this 

 worm is carnivorous, devouring for its final meal, as it would seem, 

 before it changes to its pupa state, the defenceless larva of the C. 

 Salicis. What are its previous habits — on what it subsists to at- 

 tain its present size, and how it obtains an entrance into the cell 

 of the C. Salicis 1 are interesting inquiries, requiring a more ex- 

 tended series of observations than I have as yet been enabled to 

 bestow. About one-tenth of the galls contain these larva. 



But the Cecidomyia appears not always to die unavenged. I 

 thrice observed the tenant of the willow gall to be a minute, 

 glassy-white, footless grub, .08 long, and about a third as broad ;jli 

 oval, minutely pubescent, composed of thirteen segments. Thes€,|a< 



