2O8 MAINE AGRICULTURAL EXPERIMENT STATION. 1916. 



Although the larva of each species will doubtless be found 

 to vary in a measurable degree or perceptible way from every 

 other species, it appears that these various larvae can be assem- 

 bled into five groups, collectively distinct from each other, while 

 the larvae in the group have many important points in common. 

 I have, therefore, separately described them and shall, for con- 

 venience, speak of them as types of larvae. 



STRUCTURE OF THE LARVAE. 

 I. THE APHIDOPHAGOUS TYPE OF LARVA. 



Body sub-cylindrical, flattened ventrally and much attenuated 

 anteriorly. Posterior respiratory process short, the spiracles 

 either straight or convoluted, never denticulated. Inter-spira- 

 cular ornamentation consisting of bare hairs, nodules, ridges or 

 lamella?, never of plumose hairs. Mouthparts of two ^.-shaped 

 jaws. Segmental hairs single. If prolegs present, without 

 specialized vestiture. Anterior pupal respiratory cornua appar- 

 ently wanting. 



This type of larva, named from the most characteristic habit, has 

 the posterior larval spiracles at the apex of two very short, rigid, 

 heavily chitinized, cylindrical breathing tubes which are fused mesad 

 throughout their length (except in very young larvae) never bifurcated 

 except very slightly at the extreme tip; situated terminally or on the 

 dorsum of the depressed twelfth segment. This short double tube 

 bears on its tip three pairs of slit-like spiracles elevated on radiating 

 carinae, usually nearly straight, never branched or denticulate ; and 

 a more or less prominent circular plate or "button." The in>terspiracular 

 ornamentation (between the spiracles) may consist of hairs, spines, 

 nodules, ridges or perpendicular plates, never of plumose hairs. The 

 anterior spiracles are sessile or nearly so, rounded or lunate, very 

 small. The body is elongate, slender, tapering to a point at the 

 anterior end, somewhat flattened ventrally. 



The body is wrinkled transversely and the wrinkles or folds grouped 

 in such a way as to imperfectly mark the body segments, which are 

 further indicated by the segmental spines, a transverse row of twelve 

 hairs, spine's, or bristles on each segment, sometimes obscure, some- 

 times very prominent, but always present and differentiated from the 

 remaining integumental vestiture. 



The mouth-parts consist of two V-shaped, jaw-like pieces working 

 vertically and associated spines or booklets ; which, with the terminal 

 anterior segments, are strongly retractile. 



The integument is tough but thin and more or less transparent, 

 either glabrous and papillose or closely set with minute stiff hairs 



