Pomona College Journal of Entomology 603 



mm.; IV, 0.31 mm.; V, 0.31 mm.; VI, 0.15 mm. (spur ()..'i(i mm.); total I.(J1 mm.; 

 circular sensorium at apix of article V and usual ones in the nail-like process. 

 Proihorai' — With lateral tuherelcs .-it the b.ase. Meso- and Meta-fhorax — Not dis- 

 tinctly defined. Abdomen — Robust, smooth with lateral depressions near front 

 margins, two marginal tubercles on each side, bl.iek or dark brown. Cornicles — 

 (Figure 196 E). Cylindrical, widest at base and gradually tapering to tip which 

 is slightly rimmed, imbricated, black, length 0.2 mm. Legs — Normal, hairy, col- 

 ored as in the winged form. Style — Conical, much wider at base than at apex, 

 hairy, black, half as long as cornicles, 0.1 mm. 



Young — The young apterous forms are from dull brown to black, while the 

 nymphs are reddish brown. 



Hosts — This species settles in great colonies on the tender twigs of orarge 

 and lemon trees and may entirely destroy the new top on a young tree. They 

 also feed upon the undersides of the leaves of suckers and tender shoots of old trees. 

 In not a few cases old, tough leaves are attacked by this species. The presence of 

 the insect upon the older leaves is usually recognized by the curling and tw'sting 

 of the foliage so as to form a place of protection for them on the insides (yf the 

 cup-shaped leaves. While this insect has been found feeding on Orange, Citron 

 and Camellia in Europe and on Pelea, Straussia and Coffea in the Hawaiian 

 Islands, I have been able to find it only upon citrus trees in this locality, where 

 it seems to exist during the entire year. 



Locality — Throughout the entire southern part of California. Taken by the 

 writer in San Diego, Orange, San Bernardino, Los Angeles and Ventura counties. 

 Wm. Davidson also reports it at San Jose. 



Date of Collection — Occurs in this locality during the spring and early sum- 

 mer months in abundance. Collected April 3, 1911, when most numerous. Serial 

 number 14. 



This species is easily mistaken for another small black aphis working in a 

 similar manner and nearly always associated with it on seedling t-ees, Aphis 

 gossypii Glover. It is easily distinguished from A. gassy pii, with the unaided eye, 

 by the black stigma on the primary wings as referred to above, and most easily 

 distinguished under the microscope by the third discoidal vein bei»g but once 

 branched instead of twice as in J. gossypii. 



Natural enemies — This insect is most eflfectually held in check by the two 

 internal parasites described hereinafter and by the larvae of the large Syrphid Fly, 

 Lasiophthicus pyrastri L., although the larva; of the Syrphus americanus Wied., 

 and of Allograpta obliqua Say. play an important part in this. Of the ladybird 

 beetles, Coccinella calif ornica Mann, is the most important enemy here. 



Mr. John June Davis, Mr. J. T. Monell, Prof. Theo. Pergande and Prof. Wm. 

 Davidson have aided me much in the determination of this species. 



