INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



89 



Life History. — The cabbage aphis appears with the first plants in 

 the spring and increases with such rapidity as to soon almost entirely 

 cover the host. This condition prevails throughout the early summer, 

 after which the parasites begin to reduce their numbers. During the 

 winter also colonies may be found feeding upon various plants, without 

 any interruptions, though in only limited numbers. Eggs are laid on 

 old plants. 



Distribution.— It is exceedingly common throughout the entire 

 State. 



Food Plants.— Practically all members of the family Cruciferce 

 including broccoli, cabbage, cauliflower, I satis tinctoria, kale, kohl-rabi, 

 mustard, radish, rutabaga, shepherd's purse, etc., are attacked. 



Natural Enemies.— The ladybird beetles, Hippodamia convergens, 

 Megilla maculata fuscilabris and Coccinella californica, prey to some 

 extent upon this pest. The internal parasite, Dicsretus califomicus 

 Baker 00 also attacks it. These enemies are not a factor in its control. 



THE MELON APHIS 

 Aphis gossypii Glover 



(Aphis ciicumcris Forbes) 

 (Fig. 71) 



Description.— The adult plant lice are small and very dark in color, 

 varying from yellowish to dark green, brown or black. The apterous 

 agamic female is usually dark green with often irregular lighter 

 markings on the abdomen. The nymph is somewhat lighter than 

 the apterous female. 



Life History. — The over- wintering plant lice appear early in the 

 spring, infesting all sorts of plants and often becoming a most serious 

 pest before the farmer is aware of their presence. They continue 

 to work until about the middle of the summer, when their numbers grad- 

 ually decrease and only a few hibernate or feed during the winter. 



Fig. 71. — The melon aphis. Aphis gossypii Glover. Winged and apterous females. 

 Greatly enlarged. (Author's illustration, P. C. Jr. Ent.) 



Distribution.— This species occurs throughout the entire State and 

 this is one of the most common aphids. 



Food Plants.— The foliage and young shoots of the plants are 

 attacked. On citrus trees the tender shoots are often entirely destroyed. 



""Baker, C. P., P. C. Jr. Ent. I, p. 25, 1909. 



