100 MISCELLANEOUS STUDIES 



0.1015 mm.) ; VI spur, 0.391 mm.; cornicles, 0.204 to 0.246 mm. (av. 

 0.2179 mm.) ; cauda, 0.103 to 0.119 mm. (av. 0.1084 mm.) ; hind tarsi, 

 0.136 mm. 



118. Aphis cooki Essig 



Figures 212 to 214 



Essig, Pom. Jour. Ent., vol. 2, p. 323, 1910. Aphis gossypii Glover (desc.). 

 Essig, Pom. Jour. Ent., vol. 3, p. 587, 1911 (orig. desc.). 



Record. Citrus sp., Pomona (Essig). 



In 1909, C. H. Vary, county horticultural inspector in Pomona, 

 found a few orange trees heavily infested with this aphid. Prompt 

 control measures were taken and since then it has never again been 

 observed. Essig first thought it to be Aphis gossypii Glover and de- 

 scribed it under that name. Later, however, he found it to be an 

 undescribed species, so named it Aphis c&oki n.sp. after Dr. A. J. Cook. 



119. Aphis cornifoliae Fitch 



Fitch, Cat. Homop. N. Y., p. 65, 1851 (orig. desc.). 



Records. Cornus pubescens, Sanicula mensiesii; San Francisco Bay region 

 (Davidson). 



A species comparing very favorably with this has been taken by 

 Davidson a number of times in the San Francisco Bay region. The 

 fall and winter is spent on dogwood, the summer on gambleweed. 

 Davidson writes as follows : 



This aphid [from Sanicula] certainly appears to be very close to what I have 

 called (after Gillette) cornifoliae. Moreover, I have noticed that the two plants, 

 dogwood and Sanicula, frequently grow near each other and that there appeared 

 to be a migration of alates from the former just about the time there was a 

 migration of the alates to the latter. 



This migration took place the latter part of April in 1916. 



120. Aphis crataegifolii Fitch 



Fitch, Cat. Homop. N. Y., p. 66, 1851 (orig. desc.). 

 Sanborn, Kan. TJniv. Sei. Bull. 3, p. 53, 1904 (desc.). 

 Davidson, Jour. Econ. Ent., vol. 3, p. 377, 1910 (list). 



Record. Crataegus oxycantha; San Jose, Palo Alto (Davidson). 



This has been reported more or less abundant on hawthorne in the 

 San Francisco Bay region. According to A. C. Baker this is a good 

 and distinct species and not a synonym of Aphis pomi De Geer, as 

 formerly believed. 



X 



