128 MISCELLANEOUS STUDIES 



0.731 to 0.782 mm. (av. 0.748 mm.) ; III, 0.153 to 0.187 mm. (av. 

 0.170 mm.) ; IV, 0.119 to 0.136 mm. (av. 0.1224 mm.) ; V, 0.119 mm.; 

 VI, base 0.085 mm.; VI, spur 0.136 to 0.1995 mm. (av. 0.1632 mm.) ; 

 cornicles, 0.153 to 0.1995 mm. (av. 0.170 mm.) ; cauda, 0.136 to 0.170 

 mm. (av. 0.162 mm.) ; hind tarsi, 0.102 to 0.119 mm. (av. 0.114 mm.). 



151. Aphis yuccae Co wen 



Figures 303 to 305 



Cowen, Colo. Agr. Exp. Sta., Bull. 31, p. 122, 1895 (orig. dese.). 

 Williams, Univ. Neb. Studies, vol. 10, p. 145, 1910. Aphis yuccicola n.sp. 

 (desc.). 



Records. Yucca moJuivensis; Moorpark, Ventura County, April, 1916 (F. M. 

 Trimble) ; San Diego, May, 1916. 



In April, 1916, Horticultural Inspector F. M. Trimble of Ventura 

 County sent the author a few specimens of the alate and apterous 

 viviparous females of this species, taken on Spanish dagger in Moor- 

 park. In the latter part of the next month the author found a few 

 apterae on the leaves of Spanish dagger in Golden Hill Park, San 

 Diego. There were only a few individuals present at that time, but 

 there was evidence of an earlier heavy infestation. Following are a 

 few notes to supplement Williams ' excellent description of this species. 



Ill is the longest segment of the antennae, followed by VI spur, 

 which is about three-fourths as long. IV is next, being a little over 

 one-half as long as III and about five-sixths as long as VI spur. V 

 is slightly shorter than IV and is followed closely by VI base, which 

 is about one-half the length of the spur. The usual primary sensoria 

 are present on V and VI and the accessory sensoria on VI (fig. 303). 

 The apterae have no secondary sensoria, while the alates along the 

 whole length of III (fig. 304) have about twenty-five irregularly 

 placed sensoria of irregular size. VI is without sensoria. Lateral 

 tubercles are present on the prothorax and on the first and seventh 

 abdominal segments. The cornicles (fig. 305) are long and slightly 

 tapering, being but slightly shorter than the spur of the sixth antennal 

 segment and about twice as long as the hind tarsi. The cauda (fig. 

 305) is ensiform or sickle-shaped and about three-fourths as long as 

 the cornicles. In length it is about equal to the fifth antennal seg- 

 ment and one-half again as long as the hind tarsi. 



