90 MISCELLANEOUS STUDIES 



32. VI spur shorter than III 33 



VI spur not shorter than III 34 



33. Cornicles about three times as long as cauda medlcaginis Koch 



Cornicles not three times as long as cauda 34 



34. Cauda more than one-half as long as cornicles 35 



Cauda not more than one-half as long as cornicles 38 



35. Ill with four or five fairly large semsoria oregonensis Wilson 



Ill with many irregular sensoria 36 



36. Ill with 20 or more sensoria, IV with none 37 



Ill with less than 20 sensoria, usually 14 or 15. IV usually with one or two, 



or. more sensoria euonomi Fabr. 



37. IV about one-third longer than V. Cornicles about four times as long as 



broad at base. On Heraclium spp heraclii Cowen 



IV but about one-sixth longer than V. Cornicles about three times as long 



as broad at base. On Yucca sp Yuccae Cowen 



38. A few (about 10) equal-sized sensoria on III (fig. 222). A large yellow 



species with distinct dark markings nerii Fonsc. 



About 20 irregular sensoria on III (fig. 211). Not yellow 39 



39. Cornicles slightly more than twice as long as hind tarsi 40 



Cornicles not twice as long as hind tarsi carl Essig 



40. Hind tarsi slightly longer than cauda ceanothi Clarke 



Hind tarsi shorter than cauda cornifoliae Fitch 



41. VI spur one and one-half or more times as long as III setariae Thomas 



VI spur never so much longer than III 42 



42. Ill with a few large circular sensoria (5-10) (figs. 226, 290) _ 43 



Ill with several (15 or more) irregular sensoria 45 



43. Beak reaching to or beyond third coxae. IV never with sensoria. 



gossypii Glover 



Beak not reaching third coxae 44 



44. VI spur longer than III (fig. 226). Small size pomi de Geer 



VI spur subequal to or shorter than III (figs. 289, 290). Medium to large 



size cerasifoliae Fitch 



45. Cornicles twice as long as cauda. Femora of all three pairs of legs similarly 



colored carl Essig 



Cornicles longer than cauda, but not twice as loag. Femora of first pair of 



legs pale, of second and third pair black euonomi Fabr. 



Apterous viviparous females^ 



1. Cornicles shorter than hind tarsi 2 



Cornicles equal to or longer than hind tarsi 4 



2. VI spur longer than III. White bars and bands on abdomen in life. 



albipes Oestlund 



VI spur not longer than III. Abdomen not as above 3 



3. Cornicles and cauda subequal. Beak not reaching to second coxae. Pul- 



verulent brassicae Linn. 



Cornicles shorter than cauda. Beak reaching to or beyond second coxae. Not 



pulverulent atriplicis Linn. 



is In this key only those species are included of which there are specimens in 

 the author's collection or of which there are adequate descriptions available. 

 The following species are therefore omitted: Aphis alamedensis Clarke, A. hough- 

 tonensis Throop, A. mori Clarke, A. neomexicana Cockerell, A. oenotherae Oest- 

 lund, and A. tetrapteralis Cockerell. 



