28 MISCELLANEOUS STUDIES 



0.442 mm., IV 0.255 to 0.272 mm., V 0.221 to 0.2465 mm., VI 0.255 mm. 

 (base 0.136 mm., spur 0.119 mm.), cornicles height 0.034 mm., diam- 

 eter at apex 0.034 mm., wing length 1.581 to 1.768 mm., width 0.663 

 to 0.68 mm., expansion 3.825 mm. 



8. Genus Chromaphis Walker 

 Walker, The Zoologist, p. 2001, 1870. Type Lachnus juglandicola Kalt. 



23. Chromaphis juglandicola (Kalt.) 



Figures 34, 35 



Kaltenbach, Monog. d. Pflanzenlause, p. 151, 1843. Lachnus (orig. desc.). 

 Essig, Pom. Jour. Ent., vol. 1, p. 51, 1909. Callipterus (desc. vivi.). 

 Essig, Pom. Jour. Ent., vol. 4, p. 763, 1912 (list). 

 Davidson, U. S. Dept. Agr., Bull. 100, pp. 2-19, 1914 (desc. all forms). 



Records. Juglans regia; San Francisco Bay region, southern California. 



This walnut aphis is the most abundant and injurious of the 

 species attacking walnut in California. It is more or less abundant 

 throughout the San Francisco Bay region, while in southern Cali- 

 fornia during certain seasons it is an important pest. Davidson 

 (1914) has described all the forms and studied the life history care- 

 fully, so but little comment is necessary. In 1915 the author 

 observed the young stem mothers on March 22 in Sunnyvale, Santa 

 Clara County. Three weeks later the second generation was well 

 advanced. From the first of May on, in 1916, the viviparae were 

 abundant on walnuts throughout San Diego County, from nursery 

 stock in San Diego to a few cultivated trees at Santa Ysabel (altitude 

 3000 feet). From the middle of October until well into December, 

 1916, the sexuales were found throughout Los Angeles and Riverside 

 counties. 



9. Genus Callipterus Koch 

 Koch, Die Pflanzenlause, p. 208, 1855. Type Aphis juglandte Kalt. 



The two members of this genus in California have been considered 

 heretofore as species of Monellia Oestlund (genus 10), but according 

 to Davis 6 they can not be so considered for in Monettia the wings are 

 laid flat on the abdomen when at rest. This is found only in M&nellia 

 caryella (Fitch). Incidentally it may be remarked that the species 

 known by that name in California does not have that habit, so 

 should really be placed in this genus, Callipterus Koch. However, as 

 it is identical with eastern specimens, except for this habit, the author 



6 Essig, E. O., Beneficial and Injurious Insects of California, Mon. Bull. Cal. 

 Comm. Hort., vol. 4, p. 83, 1915. 



