114 MISCELLANEOUS STUDIES 



Apterous viviparous female. The apterae are quite similar to the 

 alates except that the thorax is not dark, and that the second, third, 

 and basal three-fourths of the fourth antennal segments are pale. 

 There are no secondary sensoria (fig. 296) and no lateral tubercles 

 on prothorax and abdomen (fig. 297). The individuals are slightly 

 larger and the proportions of the antennal segments differ slightly 

 from the alates. The measurements of specimens mounted in Canada 

 balsam are as follows : 



Measurements: Body length, 1.00 to 1.04 mm. (av. 1.026 mm.); 

 width (abdomen), 0.595 to 0.629 mm. (av. 0.6064 mm.) ; antennae 

 total, 0.561 to 0.697 mm. (av. 0.6151 mm.) ; III, 0.102 to 0.136 mm. 

 (av. 0.1218 mm.); IV, 0.0765 to 0.1105 mm. (av. 0.0906 mm.); V, 

 0.068 to 0.085 mm. (av. 0.0765 mm.) ; VI, 0.595 to 0.0765 mm. (av. 

 0.068 mm.) ; spur, 0.1615 to 0.1785 mm. (av. 0.1711 mm.) ; cornicles, 

 0.0765 to 0.11 mm. (av. 0.0935 mm.) ; cauda, 0.0595 mm.; hind tarsi, 

 0.102 mm. (Description from nine specimens of apterae). It will 

 be noticed that in the apterae the antennae are but about two-thirds 

 as long as the body, while in the alates they are almost as long as the 

 body. Furthermore, in the apterae the spur of the sixth antennal 

 segment is always longer than III while in the alates it is equal to III 

 at the most, and in many cases shorter. 



131. Aphis medicaginis Koch 



Figure 189 



Koch, Die Pflanzenlause, p. 94, 1854 (orig. desc.). 

 Davidson, Jour. Econ. Ent., vol. 2, p. 302, 1909 (list). 

 Davidson, Jour. Econ. Ent., vol. 3, p. 376, 1910 (list). 

 Essig, Pom. Jour. Ent., vol. 3, p. 527, 1911 (dese.). 



Records. Medicago hispida; Stanford University (Davidson), April, 1914 

 (R W. Haegele) : Astragalus leucopsis; Nordhoff, Ventura County (Essig) : Vicia 

 faba, lima bean, Pasadena (E. E. Campbell). 



This small dark Aphis has been found occasionally in California, 

 particularly on alfalfa and beans. Such other plants as loco weed, 

 licorice, sagebrush, locust, and others are said to be hosts. The author 

 has never collected it himself, but has had access to specimens taken 

 by Essig, Haegele, and Campbell. Davidson has reared the braconid 

 fly, Lysipheebus testaceipes Cresson, from this aphid. 



