88 



INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



are dusky green. The honey-tubes are shorter than those of the 

 green apple aphis. 58 



Life History. — As in the case of many other aphids the eggs are 

 laid upon fruit trees in the fall and hatch into the stem-mothers in 

 the spring. These stem-mothers remain upon the fruit trees and 

 bring forth a brood of young which also work for a time at least 

 upon the foliage of the trees. As the winged migratory forms appear 

 they leave the trees for clover and other plants, where they remain 

 during the summer. In the fall, migrants return to the fruit trees 

 and give birth to true sexual forms which mate and the females lay 

 the over-wintering eggs. On certain plants in this State, such as the 

 German ivy or groundsel, 50 the viviparous females may exist through- 

 out the entire year. In many parts also it is doubtful if any eggs are 

 laid at all, the mature viviparous females simply continuing through 

 the winter in a more or less inactive condition. 



Nature of Work. — On fruit trees there is a slight curling of the 

 leaves in the spring, which is not nearly as serious as is caused by either 

 the green or the rosy apple aphis. Clover and other plants show little 

 or no effects of their attacks. 



Distribution. — This aphis is 

 distributed throughout the central 

 and northern parts 

 of the State. 



FoodPlants.— The 

 following plants are 

 hosts : alfalfa, Am- 

 sinckia, apple, crab 

 apple, globe arti- 

 choke, chamomile (Anthe- 

 mis), clover, cudweed 

 (Giiaphalium) , groundsel 

 (Senecio), hawthorn, pear 

 and California sage. 59 To 

 this list Davidson also 

 adds the common sun- 

 flower. 



THE CABBAGE APHIS 

 Aphis brassicw Linnaeus 



(Fig. 70) 



Description. — The 

 adult is dark green or 



vfillmvicli w i + V, no-.m/vnr „, Fig> 70 - — Tne cabbage aphis, Aphis brassicw Linn, 

 yeuu vvibll Wltn nariOW Winged and apterous females. Greatly enlarged. 



somewhat broken trans- ( Auth01 's illustration, p. c. Jr. Ent.) 

 verse brown lines across the abdomen of most of the winged and apterous 

 females. The body is entirely covered with a fine white powder. This 

 aphis collects in large, dense colonies on the food plants and is readily 

 distinguished by the whitish covering. 



"-Wilson, H. F., Bien. Crop Pest and Hort. Rept. Ore. Agrcl. Exp. Sta., p. 89, 

 "Davidson, W. M., Jr. Ec. Ent., VII, p. 133, 1914. 



