Vol.1] 



Essig. — Aphididae of California 



327 



woolly material. This bark feeder is at once distinguished by 

 the partial covering of thin white wool and the bright orange 

 cornicles. 



Pterocomma popidifoliae (Fitch). This dark gray and brown 

 species occurs plentifully on Sniix, spp., on the campus, March 

 29, 1916. Lacks the cottony covering of the preceding species. 



Tuherolachnus viminalis (Fonsc.) (fig. 16). Our largest 

 species occurring on willow and easily recognized by the gray 

 color and the large black tubercle on the back between the 

 cornicles. Abundant on the trunks and branches of various 

 willows and feeding in large compact colonies. Taken on yellow 

 willow, Sali.r Iasiaitd)'a Benth., red willow, S. lacvifjata Bebb., 



Fig. 16. Tnherolacluius viminnlis (Fonsc). Apterous viviparous females 

 on longleaf willow, Salix longifolia Mulil. Berkeley, Cal., June 10, 1916. 

 (Oritjinal.) 



longleaf willow, S. lougi folia ]\Iuhl., and arroyo willow, S. lasio- 

 lepis Benth., on the campus and at Berkeley and on the arroyo 

 willow at Rutherford. California, June 21, 1916. 



Lachuus pini-radiatac Davidson. This very dark green 

 species is partially covered with a thin whitish woolly secretion 

 and usually feeds in colonies in rows on the pine needles. Taken 

 on the campus in small numbers on yellow pine, Finns pondcrosa 

 Dougl., January 1 and JMarch 11, 1915. 



Lachnus tujafilinns Del Guercio. A robust brown and grayish 

 species occurring in dense colonies on the twigs of common arbor- 

 vitae, Thuya occidentalis Linn. Received from Chas. B. Weeks, 

 Red Bluif, California, February 8, 1916. 



Nectarosiphmn ruhicola (Oestlund). A large normally green 

 species occurring in colonies on the undersides of the leaves of 



