78 



INJURIOUS AM) BENEFICIAL INSECTS OF CALIFORNIA. 



THE BLACK CITRUS PLANT LOUSE 



Toxoptera uurantiw Koch 



(Fig. 60) 



Description.— This is a small dull-black plant louse, scarcely over 

 1-16 inch in length. The apterous forms often appear brown, while 

 the young are a decided reddish-brown to black. Some of the adults 

 are somewhat shiny black and have been mistaken for the black 

 peach aphis (Aphis persicce-niger) . It is easy to distinguish the winged 

 individuals of this species by the very dark and prominent stigma 

 and the single branch of the third discoidal vein. 



H 



Fig. 60. — The black citrus plant louse, 

 apterous females. Greatly enlarged. 



Toxoptera aurantim Koch. Winged and 

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



Life History.— This species may be found in the citrus groves 

 throughout the entire year, all stages being present. The greatest 

 numbers occur during the spring months, when all the new growth 

 may be destroyed on the young trees by them. Older trees are also 

 attacked. The presence of the insects on the larger and older leaves 

 is easily told by their curled appearance, a condition produced by 

 the plant lice. The eggs have not been observed but they are prob- 

 ably laid on the citrus trees in the late fall. 



Distribution. — This aphid occurs throughout the entire citrus grow- 

 ing section of the State. It is especially abundant in the southern 

 coast counties. 



Food Plants. — This pest attacks camellia, citron, coffee, grapefruit, 

 lemon, Olea straussia, orange and tangerine. 



Natural Enemies.— This insect would be a far greater pest were 

 it not for its many natural enemies. Two internal parasites, Aphidhis 

 testaccipes Cr. and Charips xanthopsia (Ashm.), have been bred from 

 adult plant lice, while the California ladybird beetle (Coccinella cali- 

 fornica Mann.) and the larva? of three syrphid flies (Allograpta obliqua 

 Say. Syrphus americawus Wicd. and Syrphus pyrastri Linn.) have been 

 observed in large numbers feeding upon it. The second internal para- 

 site is probably secondary. 



THE WOOLLY APPLE APHIS 



Eriosoma lanigera (Hausmann) 



(Schizoneura lanigera Hausmann) 



(Fig. 61) 



Description. — To the average orchardist this insect is of too com- 

 mon occurrence to need any suggestions for its identification. The dark 

 red or purplish loose covered with the long white cottony wax or floccu- 



