Williams' "The Aphididae of Nebraska" 37 



Only wingless females on slide. Beak long, reaching to the 

 coxae of the third pair of legs. Antennal segment III bearing 4 

 to 9 rather large but inconspicuous circular sensoria, more or 

 less in a row, and usually on the basal tw^o thirds of the segment. 

 Measurements of the segments as follows : 



Cornicles very small and Chaitophorus-like; length, 0.0355 

 mm, width at apex about equal to length, width at base, 0.053 "^"i- 



Another slide bearing this species is labeled " Cryptosiphum 

 canadensis n. sp. No. 161. On Artemisia canadensis. War Bon- 

 net, 6/24, '90." 



Camera lucida drawings of the head, antenna and cornicle 

 shown on Plate I, figs. 10 and 11. 



EXPLANATION OF PLATES 



Pemphigus alnifoliae Williams, PI. I, figs, i, wing; 2, antenna, of winged 

 viviparous female. 



P. balsamifera Williams, PI. I, figs, 3, fore and hind wing; a, branching 

 of veins of hind wing in some specimens; 4, antenna, of winged viviparous 

 female. 



Lachnus ponderosa Williams, PI. I, figs. 5, head and antenna; 6, hind 

 tarsus; 7, cornicle; 8, wing, of winged viviparous female; 9, antenna of 

 wingless viviparous female. 



Microsiphum canadensis Williams, PI. I, figs. 10, head and antenna; 

 II, cornicle, of wingless viviparous female. 



Chaitophorus bruneri Williams, PI. II, figs. 12, head and antenna; 13, 

 style; 14, cornicle, of wingless viviparous female. 



Ch. viminalis Monell (salicti Schrank- Williams), PI. II, figs. 15, antenna 

 of wingless viviparous female; 16, antenna; 17, cornicle; 18, style, of 

 winged male; 19, hind tibia; 20, cornicle, of wingless oviparous female. 



Mclaiwxantherium bicolor Oestlund, PI. II, fig. 21, cornicle of wingless 

 viviparous female. 



Mel. smithae Monell, PI. II, fig. 22, cornicle of wingless oviparous 

 female. 



Aphis artemisicola Williams, PI. II, figs. 22, head and antenna ; 24, 

 cornicle; 25, style, of wingless viviparous female. 



289 



