90 



INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



Vines are injured throughout. The recorded food plants are : aspara- 

 gus, begonia, buckthorn, catalpa, citron, cotton, cucumber, dock, 

 dogwood, gourd, grapefruit, hop, hydrangea, iron-weed, jimpson weed, 

 lambsquarters, lemon, malva, morning glory, muskmelon, orange, pear, 

 pepper grass, pigweed, plantain, shepherd's purse, spinach, sugar 

 beet and watermelon. 



Natural Enemies. — The ladybird beetles, Hippodamia convergens, 

 Guer., Coccinella calif ornica Mann., Scymnus sordidus Horn, Cycloneda 

 sanguined (Linn.) and many others, and the larvas of the green lace- 

 wing, Chrysopa californica Coq. are predaceous, while the hymenop- 

 terous parasites Aphidius testaceipes (Cr.) and Charips xantJiopsis 

 (Ashm.) are parasitic upon this aphis in California. The last is prob- 

 ably secondary. 



THE BUR CLOVER OR COWPEA APHIS 



Aphis medicaginis Koch 

 (Fig. 72) 



Description. — The mature females are of medium size and shiny 

 black color. The immature forms are often reddish-brown. The abdo- 

 men of the winged form is usually dull-brown or greenish with dark 

 transverse bands on the dorsum. Very noticeable characters of both 

 apterous and winged lice are the yel- 

 low or whitish legs, which are dark 

 only at the joints, and the light basal 

 half of the antennas. These mark- 

 ings, together with the short black 

 honey tubes of the shiny black adults, 

 usually serve to distinguish this form 

 from all others. The length averages 

 about 1-12 inch. 



Life History. — The life history has 

 not been worked out in this State, 

 exeept to observe the summer forms. 

 The eggs are laid in the fall on locust. 



Nature of Work.— The lice collect 

 in large colonies upon the stems and 

 leaves of the host plants, causing them 

 to become pale and sickly. The attacks usually do not continue long 

 enough to cause serious damage. 



Distribution.— This is a very common aphis throughout the entire 

 State. 



Food Plants.— The bur clover or cowpea aphis attacks alfalfa, 

 apple, bean, Caragana aborescens, clover, cowpea, dandelion, dock, 

 lambsquarters, wild liquorice, loco-weed, clammy locust, false-mallow, 

 meadow-grass, Melilotus italica, mustard, orange, pear, pepper-grass, 

 primrose, rhubarb, senna, shepherd 's-purse, Sophora and tansy. There 

 is some confusion regarding the identity of this louse, so that some of 

 the plants listed may prove to be wrongly credited as hosts of this 

 species. 



Fig. 72. — The bur clover or cow- 

 pea aphis, Aphis medicaginis Koch. 

 Greatly enlarged. (Author's illus- 

 tration, P. C. Jr. Ent) 



