﻿120 SEVENTH ANNUAL KEPORT 



Deep yellow Form, with longer, roughened Tubercles (b) : — 



As frequent as a in July, and diflering in the deeper color, inclining to brown, and in 

 the greater length, irregidarity, and darker color of tubercles : these tubercles are generally 

 longest on middle body, and appear quite dark under a pocket lense ; under the microscope 

 they appear quite roughened with fleshy points from the sides toward the swolleu base, and 

 around the somewhat blunt, and sometimes slightly swollen tip. 



Black Form, with very long Tubercles (c) : — 



NVith the body dai-k brown and the tubercles almost black; the dorsal ones, especially in 

 middle of body, very long— half the diameter of body— slender, gradually tapering to tip, 

 the lateral ones and some of the dorsal ones, less tapering and half as long. Antennse with 

 the third joint quite long and slender. 



Pupa, normal Form (d) : — 



With the tubercles prominent, and the pale, mesothoracic portion occupying more of the 

 body than in vastatrix. 



Smooth Form {e) : — 



More elongate, paler, without tubercles. Only occasionally met with. 



Winged, agamous ^ (/) : — 



With the dai'k, mesothoracic band much as in vastatrix; the wings more slender, and some- 

 what more fuliginous, with the costal angle more produced and blunt, and the hook larger on 

 secondaries; the antennas wath the third joint and the horny parts proportionally longer. 

 Also presenting two forms of body and wings as in vastatrix. 



Male (g) :- 



Not much larger than the newly-hatched larva; without tubercles, having but a few faint, 

 hair-like points in their stead : the two tarsal claws distinct, but the basal jomt of tarsus obso- 

 lete: the antennae simple (at least there is, if ans'thing, but the faintest trace ot a small plate 

 at tip): no sign of mouth-parts; the venter sometimes shows two opaque spots about middle, 

 and the penis is quite conspicuous, the external parts seeming to consist of a tubercle which is 

 bulbous at base, but pointed at tip, and of two dusky, apparently horny processej which rim 

 down each side as if to jirotect it.* 



(The eight specimens obtained Irom winged Q, which I have mounted, all seem to be of one 

 sex, unfortimately, and no $ is among them.) 



Newly-hatched Larva (h) : — 



Nearly smooth, with dark limbs and eyes, the tubercles indicated by slight swellings, which 

 are, however, surmounted with a longer fleshy hair. The proboscis reaching beyond tip of 

 abdomen. 



Hibernating Larva (i) : — 



With the tubercles quite large, smooth, and surmounted at tip with a single spinous hair. 



The truo female yet remains to be described. Most entomoioorists would consider 

 the forms c and e as specifically distinct from Rileyi — so abdormal do they appear : but 

 a careful Summer's study of our Oak Phylloxera leads me to the conclusion that they 

 are but forms of one and the only species occurring on the Oak in America. In fact, 

 the polymorphism of these insects is not yet sufliciently appreciated even among 

 entomologists ; and 1 am strongly inclined to believe that the discussion about the dif- 

 ferent species occurring on Oak in Europe, is based, iu great part, on the variations of a 

 single species. The tubercles in Rileyi vary somewhat with each molt, and I have 

 come to look upon the paleness or intensity of color as of little specific value. 



At lea^t live generations intervene from the mothers which hibernate to the winged 

 form appearing first in July; and, from having enclosed some of the first winged 

 females in niuslin bags covering leaves that were carefully freed of all insect life; and 

 liaving ^ubsequentlj' found such leaves infested with the ordinary agamous female 

 with her progeny in all stages, there is reason to believe that the winged mothers may 



♦These males are so veiy minute, that the generative organ is not easily resolved, and presents a 

 diflerent appearance, accorduig to position on the slide; but in most ci-ses I could discern these dusky 

 ))roccsses with sutlicient distinctness. 



