[Assembly 
Variety b, nigricollia. The neck not green, bnt of the same blaek color as th« 
head and thorax. Comwson among aged individuals. 
c, thoracica. The thorax dull green, with a black band forward of its 
middle. Young. 
i, fulviventria. The abdomen pale dull yellow instead of green. 
t, nigriventria. The abdomen greenish blaek, with the row of blaek dots 
along each side, indistinct. 
/, immaculata. The abdomen without any dots or darker colored marks. 
g, obsoleta. The lateral row of black dots faint and scarcely perceptible, 
h, triaeriata. A row of black dots along the middle of the back, as well 
as upon each side of the abdomen. 
«, bivincta. Two black bands towards the apex of the abdomen, on its 
upper side. 
j, tergata. Abdomen above, with two black bands towards its tip, and 
three rows of black dots anteriorly. 
Several specimens of Plant-lice which I gathered from the 
leaves of Apple trees, in Mercer county, Illinois, upon the 4th 
day of October last, and which at the time of capturing them I 
supposed were varieties merely of the common species which we 
have been considering, prove on examination to pertain to a dif¬ 
ferent species. They are a size larger and of a shining black 
color throughout. In the common species the legs are uniformly 
pale with black feet and knees, the preserved specimen showing 
this character almost as distinctly as living individuals; in these 
specimens on the contrary the legs are entirely black, or at most 
brownish yellow at their bases in some instances. The wing- 
veins moreover diifer notably from those of .8-phis Mali in several 
points. They are more slender, and the fourth vein is relatively 
shorter and more strongly curved through its whole length. In 
oonsequence of this curvature it is nearer to the second fork at 
its base than at its tip. Two-thirds of the specimens which were 
captured at that locality coincide with each other in these differ¬ 
ences. This fact would indicate this to be a more common species 
upon the Apple trees in Illinois than the Aphis Mali; but its 
darker color and larger size rendering it more conspicuous than 
that species may have occasioned a disproportionately large num¬ 
ber of this species to be gathered. It may appropriately be named 
the Apple-leaf louse (Aphis Mulifolia). The specimens show the 
following marks in addition to what has already been stated : 
The Apple-lea* louse measures 0.15 to the tips of its wings. The third vein of 
t efore wings is but slightly abortive at its base. The second and third veins ars 
