88 MISCELLANEOUS STUDIES 



29. Genus Aphis Linn. 



Linnaeus, Syst. Nat., 1748. Type Aphis rumicis Linn. 

 KEY TO CALIFORNIA SPECIES 

 Alate viviparous females 



1. Abdomen with floceulent masses of wax. Antennae considerably shorter than 



body, and VI spur shorter than III alamedensis Clarke 



Abdomen without such floceulent masses of wax (except perhaps Aphis cooki 



Essig) _ 2 



2. Antennae one and one-half times as long as the body, or more. 



houghtonensis Throop 



Antennae not so much longer than body; when longer, which is seldom, but 



slightly so 3 



3. Abdomen pale yellowish green. Found only on Moms sp inori Clarke 



Abdomen darker being black, dark green, yellow. Not found on Moms sp. 4 



4. Abdomen dark-green with an orange band between the cornicles. 



augelicae Koch 



Abdomen without such an orange band between the cornicles (sometimes there 



is a slight orange or reddish coloring between the cornicles of the apterae 

 of Aphis avenae Fabr., but it is not constant) 5 



5. Abdomen sage-green with faint lateral spots. Ill with apical one-half con- 



spicuously darkened and with six large sensoria. VI spur less than one-half 

 as long as III. On Atriplex spp tetrapteralis Cockerell 



Not with above combination of characters 6 



6. IV with secondary sensoria (fig. 244) 7 



IV without secondary sensoria (fig. 204) 27 



7. Cornicles and hind tarsi subequal 8 



Cornicles considerably longer than hind tarsi 17 



8. VI spur shorter than III 9 



VI spur equal to or longer than III '. 13 



9. Cornicles short and tapering 10 



Cornicles short and incrassate pseudobrassicae Davis 



10. V with secondary sensoria. Body slightly pulverulent cooki Essig 



V without secondary sensoria. Body not pulverulent 11 



11. Less than 12 secondary sensoria on III, arranged in a more or less even line 12 



About 20 to 25 secondary sensoria on III, arranged irregularly along segment 



(fig. 244) senecio Swain 



12. Ill with 9 to 12 sensoria. V and VI base subequal, each being shorter than 



IV lithospermi Wilson 



Ill with 5 to 9 sensoria. IV and V subequal, each being longer than VI 



base viburnicolens n.sp. 



13. Cornicles shorter than hind tarsi. A large black species in life being marked 



with white bars and cross bands on the abdomen albipes Oestlund 



Cornicles and hind tarsi subequal. Body color greenish 14 



14. Root-infesting species. Antennae short, scarcely reaching the middle of the 



abdomen mlddletonii Thomas 



Aerial species. Antennae reaching to base of the cornicles, or as long as 



body 15 



15. Cornicles incrassate. A medium-sized species pseudobrassicae Davis 



Cornicles cylindrical and tapering slightly. A smaller-sized species 16 



