A SYNOPSIS OF THE APHIDIDAE 19 



This is a common species of aphid on birch (Betula spp.) in the 

 San Francisco Bay region. In the early part of March the eggs begin 

 to hatch. In 1915 at Stanford University eggs began to hatch on 

 March 8, the process continuing for several days. A month later 

 both alate and apterous females were quite abundant; the alate 

 females being undoubtedly the stem mothers, the apterae belonging 

 to the second generation. Viviparous generations appeared through- 

 out the summer. During August the sexes, alate males and apterous 

 oviparous females, occurred. In 1914 the sexes and sexupara were 

 noticed on August 28. Egg laying occurred shortly afterward, the 

 eggs being laid in the crotches of the twigs and under the curled 

 edges of the bark. Birch is the only recorded host plant. 



5. Genus Euceraphis Walker 



Walker, The Zoologist, p. 2001, 1870. Type Aphis letulae Koch. 

 KEY TO CALIFORNIA SPECIES 



1. Body light green; third joint of antennae with about 13-18 sensoria on basal 

 one-half (fig. 39) giUettei Dvdn. 



Body yellow with dark markings on head and thorax, and often with as 

 many as eight black transverse stripes on the abdomen (the number varies 

 between none and eight) ; third antennal segment with 19-25 sensoria 

 (fig. 40) betulae (Koch) 



7. Euceraphis betulae (Koch) 



Figures 29, 40 



Koch, Die Pflanzenlause, p. 217, 1855. Callipterus (orig. dese.). 

 Davidson, Jour. Econ. Ent., vol. 5, p. 405, 1913 (desc. ovi. female). 

 Davidson, Jour. Econ. Ent., vol. 7, p. 129, 1914 (desc. stem mother). 



Records. Betula sp. : Oakland (Davidson); Palo Alto, March to April, 1915. 



Davidson lists this species, describing the stem mother and 

 oviparous female from the San Francisco Bay region. The author 

 found it in Palo Alto during March and April, 1915, on Betula alba. 

 According to Davidson the stem mothers hatch from the eggs about 

 the middle of February, feeding on the stems until the leaves open in 

 March. The viviparous generations occur during the summer. He 

 took the oviparous females in November. His description of the stem 

 mother gives three dusky transverse bands on the abdomen. The 

 author has found this to be variable, the number ranging from none 

 to eight. 



