56 APPLE LEAVES — LEAF-LOUSE DESCRIBED. 



Variety b, nigricollis. The neck not green, but of the same black color as 

 the head and thorax. Common among aged individuals. 



c, thoracica. The thorax dull green, with a black band forward of 



of its middle. Young. 



d, fulviventris. The abdomen pale dull yellow instead of green. 



e, nigriventris. The abdomen greenish black, with the row of 

 black 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 per- 

 ceptible. 

 h, triseriata. A row of black dots along the middle of the back,. 



as well as upon each side of the abdomen, 

 i, bivincla. Two black bands towards the apex of the abdomen, 



on its upper side. 

 j, iergata. Abdomen aboye, with two black bands towards its tip r 

 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 of 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 differ notably from those of Aphis Mali in several 

 points. They are more slender, and the fourth vein is relatively 

 shorter and more strongly curved through its whole length. In 

 consequence 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 dark- 

 er color and larger size rendering it more conspicuous than that 

 species, may have occasioned a disproportionately larger num- 

 ber of this species to be gathered. It may appropriately be named 

 the Apple-leaf louse {Aphis Malifolicc). The specimens show the 

 following marks in addition to what has already been stated : 



The Apple-leaf louse measures 0.15 to the tips of its wings. The third 

 vein of the fore wings is but slightly abortive at its base. The second and third 



