The Aphididae of Nebraska 49 



Winged viviparous female: Head black. Thorax chiefly black above. 

 Abdomen pale green, faintly bluish at the sides, with three marginal spots 

 on each side preceding larger spots which surround the bases of the honey 

 tubes. Antennae chiefly black. Honey tubes black. Tail green, edged 

 with black. Segments behind the tail dark-edged. Head and thorax be- 

 neath chiefly black. Abdomen pale green, with two transverse black marks 

 preceding the tail. Legs pale at their articulations ; middle part of tibiae 

 often pale. Beak chiefly black. Body more slender than that of the 

 female of the root form. Antennae rather long; IV and V each longer 

 than VI.' Honey tubes moderately long, swollen in the middle. Length 

 of body 2 mm., width 0.87 mm., antennae about 0.85 mm., honey tubes 0.20 

 mm., to tip of wings about 3.35 mm. (Garman). 



The root form was found at Weeping Water, June, 1889, on 

 the roots of corn, so plentiful as to destroy a large part of five 

 acres of grain. The corn was just coming through the ground 

 or the largest but one or two inches high. The lice were clus- 

 tered along the young roots and stalks under the ground in great 

 numbers, causing the stalks to wilt and shrivel up. The first 

 notice of the presence of lice at a hill of corn was invariably given 

 by the appearance of a colony of ants (Lasius alienus Forst. ?), 

 which are responsible principally for the rapid spread of the lice 

 over the field. 



The aerial form was found in abundance at Weeping Water in 

 July and August, 1890, on corn and sorghum, generally more 

 plentiful on the latter. They were generally a little larger than 

 Garman's specimens, and the honey tubes were not so much 

 swollen ; in many cases (in both winged and apterous forms) they 

 were not swollen at all. These lice are destroyed by the larva of 

 a Syrphus fly, which seemed to be quite effectually keeping them 

 in check. Professor Forbes, who has been experimenting on the 

 life history of this aphis for some years past, expresses doubt as 

 to these two forms belonging to the same species. He has as 

 yet been unable to establish a complete connection. 



Specimens of the " aerial form " in the collection of the Univer- 

 sity of Nebraska (nos. 72, 73). 



59. Aphis malvae Walker. 



Walker, Cat. Horn. Brit. Mus., IV, p. 970 (1852). 

 Koch, Die Pflan., p. 125, figs. 169, 170 (1854). 



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