18 



perceptible numbers on young grain, it appears probable that one or 

 another generation, descendants of the migrants from grain, produces 

 a sexual generation and consequent eggs on some kind of grass, which 

 may hatch during the fall of the same year instead of the following 

 spring, in time to produce a winged generation. This last probably 

 re-migrates to young winter wheat, to restock it with lice, and many 

 would undoubtedly perish during the cold and wet season, though 

 enough of them would survive to reproduce when the climatic condi- 

 tions become more favorable. 



The whereabouts of the species after leaving the grain, the hiding 

 place of the sexes and their eggs, and the reappearance on grain, are 

 highly interesting and important questions, which entomologists of 

 infected sections should strive to solve for the benefit of those engaged 

 in the cultivation of small grain. 



DESCRIPTION OF THE SPECIES. 



Apterous female. — Length 1-1. 8 mm ; color yellowish green and slightly pruinous, the 

 median line darker green, the head and prothorax somewhat paler than the rest of 

 the body. Eyes black. Antenna? black, the two basal joints and more or less of 

 the third joint at base yellowish. Legs yellowish, the tibia 1 brownish toward the 

 apex, tarsi black; nectaries greenish and frequently with a dusky tinge, their apex 

 black. Tail dusky. The general color of the larva? and pupse is like that of the 

 apterous female. Wing pads of pupa dusky to black. Antenna? slender and about 

 one-half the length of the body. Nectaries slightly tapering, reaching to or slightly 

 beyond the end of the body. Tail slender, somewhat constricted about the middle, 

 and about two-thirds the length of the nectaries. There is a distinct fleshy tubercle 

 each side of the prothorax and similar tubercles along both sides of the abdomen. 



Migratory female. — Expanse of wings 5-7 mm ; length of body 1.5-2 mm . General color- 

 ation of the abdomen as in the apterous forms; head brownish yellow; the eyes brown; 

 antennae, thoracic lobes, the posterior margin of the scutellum and the sternal plate 

 black; the two basal joints of the antenna? yellowish green; legs yellow, the femora more 

 or less dusky, the posterior pair darkest; apex of tibiae and the tarsi black; nectaries 

 and tail yellowish, the latter changing gradually to dusky or black toward the end; 

 wings transparent; costa and subcosta yellow; the stigma somewhat paler, its inner 

 edge and the veins black. Third discoidal vein with but one fork. Antenna? long 

 and slender, reaching nearly to the end of the body, the third joint provided with 

 3 to 7 sensoria. Nectaries, tail, and lateral tubercles, as in the apterous females. 

 (See PI. I.) 



NATURAL ENEMIES. 



As natural enemies of this species in Europe, Rondani mentions 

 Scymnus Jf-pustulatus Fab., a small Coccinellid or ladybird, the adult 

 and larva? of which feed upon the lice; Paragus coadunatus Rondani, 

 a two- winged Syrphid fly, whose larva preys extensively upon all 

 kinds of plant-lice; and a minute hymenopterous insect, Aphidius 

 aphidimi L., a true internal parasite. 



Of the most effective predaceous insects which have been observed 

 to feed upon this grain aphidid in the infested regions of the United 

 States, the following may be mentioned: Two ladybirds, Hippodcmiia 



