METAMORPHOSIS OF BARK LICE 



627 



as are the wing-pads ; the front pair of legs are extended forward. " If dis- 

 turbed, they twist and bend their bodies quite vigorously." The pupa state lasts 

 two or three weeks. A similar pupa is that of Icerya 

 rosai. (Riley and Howard.) 



The metamorphosis of Aspidiotus perniciosus is of 

 interest. The male nymph differs much after the first 



FIG. 580. Pupa obtecta of Diptera: a, Ptychoptera; b, Tabanus 

 atratus; c, Proctacanthas philadelphicus; d, Midas olavatus. 



FIG. 581. Pupa libera 

 of Icerya purchasi, ven- 

 tral view. After Riley, 

 Insect Life. 



inoult from the female, having large purple eyes, while the female nymph 

 loses its eyes entirely. It passes into what Riley terms the pro-pupa (Fig. 582, 

 ft), in which the wing-pads are present, while the limbs are short and thick. 

 The next stage is the "true pupa" (Fig. 582, c, d), in which the antennae and 

 legs are much longer than before. There is no waxy cocoon, but only a case 



FIG. 582. Aspidiotus perniciosus, development of male insect : a, ventral view of larva after 

 first moult; b, the same, after second moult (pro-pupa stage); c and d, true pupa, ventral and 

 dorsal views. All greatly enlarged. After Riley. 



or scale composed of the shed larval skin, i.e. "with the first moult the shed 

 larval skin is retained beneath the scale, as in the case of the female ; with the 

 later moultings the shed skins are pushed out from beneath the scale," and when 

 they transform into the imago they "back out from the rear end of their 

 scale." 



