84 MISCELLANEOUS STUDIES 



to six inclusive, the legs, except the tarsi and tips of the tibiae, the 

 cauda, and the cornicles, except the tip, are all luteous. Sensoria are as 

 follows : on V and VI the usual primary sensoria, on VI the accessory 

 sensoria, and on III (fig. 278), from nine to eleven small, circular 

 irregularly placed secondary sensoria. IV is without sensoria. The 

 antennae are considerably longer than the body, the spur and III 

 being subequal and the longest segments. Sometimes the spur is 

 slightly longer than III. V is about one-half as long as III or the 

 spur, and about four-fifths as long as IV. I and VI are subequal, 

 being about one-seventh as long as the spur. The cornicles (fig. 284), 

 are clavate, quite large, usually being slightly more than one-fifth 

 the length of the body and over three times the length of the hind 

 tarsi. The cauda (fig. 285) is long, sickle-shaped, and a little more 

 than one-half as long as the cornicles. 



Measurements : Body length, 1.7 to 2.18 mm. ; width of abdomen, 

 0.82 to 1.73 mm.; antennae total, 2.32 to 2.48 mm.; Ill, 0.646 to 

 0.714 mm. ; IV, 0.391 to 0.425 mm. ; V, 0.323 to 0.34 mm. ; VI, 0.102 

 mm. ; spur, 0.646 to 0.782 mm. ; cornicles, 0.459 to 0.493 mm. ; cauda, 

 0.238 to 0.272 mm.; hind tarsi, 0.136 to 0.153 mm. The average 

 measurements are as follows : body length, 1.87 mm. ; width, 0.99 mm. ; 

 antennae total, 2.39 mm. ; III, 0.674 mm. ; IV, 0.408 mm. ; V, 0.334 

 mm. ; VI, 0.102 mm. ; spur, 0.7099 mm. ; cornicles, 0.473 mm. ; cauda, 

 0.255 mm. ; hind tarsi, 0.1445 mm. 



103. Rhopalosiphum nervatum Gillette 



Figures 166, 169, 171 



Gillette, Can. Ent., vol. 40, p. 63, 1908 (orig. desc.). 



Davidson, Jour. Econ. Ent., vol. 3, p. 378, 1910. B. arbuti, n.sp. (desc.). 



Davidson, Jour. Econ. Ent., vol. 7, p. 134, 1914 (list). 



Records. Arbutus menziesii; Stanford University, San Jose, Walnut Creek 

 (Davidson); Sacramento (Essig) ; Stanford University, February to May, 1915; 

 Berkeley, September, 1915: Arbutus unedo; Eedlands, February, 1917; Bosa spp. ; 

 Walnut Creek (Davidson) ; Berkeley, February, 1915 (Essig). 



In 1910 Davidson described a species of Rhopalosiphum, which he 

 named arbuti, from specimens taken on madrone in the vicinity of 

 Stanford University. Since then it has been found quite commonly 

 on madrone throughout the San Francisco Bay region, and once on 

 a strawberry tree in Silva Park, Redlands. It was noticed by the 

 author that the alate females were very scarce at all times, although 

 the apterae and nymphs were often quite abundant. Later, when 



