HOW TO KNOW THE IMMATURE INSECTS 

 7b. Hind legs not fitted for leaping 8 



8a. Scale-like insects, with waxy filaments around lateral margins; 

 antennae inconspicuous. Fig. 382 Family ALEYRODIDAE 



The common name, whitefly is de- 

 rived from the covering of whitish 

 powdery wax on the body of the 

 adults. The yoxmg produce quanti- 

 ties of honeydew. The greenhouse 

 whitefly, Trialeurodes vapoiaiioTum 

 (Westwood) is cosmopolitan and a 

 general feeder. 



Fig. 382. Aleyrodes sp. : a, dor- 

 sal aspect; b, lateral aspect. 



8b. Not as 8a 9 



9a. Cornicles usually present. Fig. 383 Family APHIDIDAE 



COf{^ICJLt- 



Fig. 383. Green peach 

 Myzus persicoe (Sulzer) : 

 instar; b, 3rd instar. 



aphid, 

 a, 2nd 



About 2,000 species have been de- 

 scribed. The aphids have a compli- 

 cated life history which is character- 

 ized by an alternation of partheno- 

 genetic generation with a sexual gen- 

 eration. Moreover, they have alter- 

 nations of winged and wingless 

 forms. The host plants are also 

 changed in different seasons. 



9b. Cornicles always wanting. Fig. 384 Family PHYLLOXERIDAE 



This family is closely related to the 

 aphids. They are often red, orange 

 or yellow and are frequently cover- 

 ed with wax. The grape phylloxera 

 which feeds on the leaves and roots 

 of some common grapes is a well- 

 known species. 



Fig. 384. Phylloxera spp., root- 

 inhabiting form. 



139 



