80 MISCELLANEOUS STUDIES 



aphid may live the entire year upon hops, or on plum, generation after 

 generation of parthenogenetic females being produced. 



99. Phorodon scrophulariae Thomas 



Thomas, Ann. Eep. 111. St. Ent., vol. 8, p. 72, 1879 (orig. desc.). 

 Clarke, Can. Ent., vol. 35, p. 252, 1903 (list). 



Eecord. Scrophularia sp., Berkeley (Clarke). 



This is a doubtful species, reported by Clarke as present on 

 Scrophularia in Berkeley, and by Dr. Thomas in 1879 on a species 

 of plant which he thought to be Scrophularia in Illinois. Since 

 Clarke's record it has never been found, although Morrison states 

 that he has spent considerable time examining the common Scrophu- 

 laria plants in the vicinity of Stanford University, but to no avail. 

 The author attempted to find it many times in the vicinity of San 

 Diego during 1916, and in the vicinity of Riverside in 1917, with no 

 success. 



28. Genus Rhopalosiphum Koch 

 Koeh, Die Pflanzenlause, p. 23, 1854. Type Aphis persicae Sulz. 



This genus is very closely related to Myzus, and is distinguished 

 only by the shape of the cornicles. This distinction is variable, how- 

 ever, as in some species certain forms have the clavate cornicles of 

 Rhopalosiphum while other forms have the cylindrical cornicles of 

 Myzus. This is particularly true in the case of Rhopalosiphum 

 persicae (Sulz.) and Myzus braggii Gillette. However, most aphidol- 

 ogists separate these two genera, so the author feels that it is best 

 to do so. 



KEY TO CALIFORNIA SPECIES 



Alate viviparous females 



1. Ground color dark (olive-green, wine, brown, and so forth) 2 



Ground color light, usually green (this does not refer to the dark markings 



on head, thorax, or abdomen, but rather to the ground color of the 

 abdomen) 4 



2. Wing veins with smoky borders and tips (fig. 164). IV with a few small 



sensoria violae Pergande 



Wing veins without smoky borders or tips, and IV without sensoria. 



rhois Monell 



3. Antennae distinctly tuberculate, with sensoria on both III and IV (figs. 170, 



279) 4 



Antennae not tuberculate, and IV without sensoria, or at most with but a 



few small ones (figs. 167, 168) 5 



