20 THE LIFE-STORY OF INSECTS [CH. 



points are especially noteworthy. Virgin reproduc- 

 tion recurs regularly, parthenogenetic broods being 

 succeeded by a single sexual brood. A winged parent 

 brings forth young which remain always wingless, 

 and wingless adults produce young which acquire 

 wings. The wings are developed, as in the cock- 

 roach, from outward and visible wing-rudiments. 



A family of Hemiptera, related to the Aphidae 

 and equally obnoxious to the gardener, is that of the 

 Coccidae or scale-insects. These furnish an excel- 

 lent illustration of features noticeable in certain 

 insect life-histories. In the first place, the newly- 

 hatched young differs markedly from the parent in 

 the details of its structure. A young coccid (fig. 7 c) 

 is flattened oval in shape, has well-developed feelers 

 (fig. 7 d) and legs, and runs actively about, usually 

 on the leaves or bark of trees and shrubs, through 

 which it pierces with its long jaws, so that it may 

 suck sap from the soft tissues beneath. After a time 

 it fixes itself by means of these jaws and the cha- 

 racteristic scale or protective covering, composed 

 partly of a waxy secretion and partly of dried excre- 

 ment, begins to grow over its body. The female loses 

 legs and feelers, and never acquires wings, becoming 

 little more than a sluggish egg-bag (fig. 7 e). The 

 male on the other hand passes into a second larval 

 stage in which there are no functional legs, but 

 rudiments of legs and of wings are present on 



