THE OPEN TYPE OF WING-GROWTH 87 



small but prominent compound eyes at the sides and two 

 ocelli on the crown, bears a pair of feelers usually with seven 

 segments and of the aphid type. The prothorax is short, the 

 mesothorax large and convex with a pair of comparatively 

 ample, rounded wings, with reduced nervuration and snowy- 

 white in hue ; the hind wings, similar in appearance, are some- 

 what shorter and narrower than the forewings. The legs are 

 slender with two-segmented feet, each foot carrying two claws 

 and a bristle-like median process (empodium). The male's 

 abdomen has a pair of conspicuous claspers ; that of the 

 female tapers to the tail-end whence project the pointed 

 process of the ovipositor. Frequently these insects are 

 partially covered with a white, waxy secretion in the form of 

 long threads (Fig. 47 a). The colour of the cuticle is com- 

 monly yellowish. 



The eggs (Fig. 47 c) laid by the female Aleyrodes are remark- 

 able for the long stalks by which they are fastened to a 

 leaf of their food-plant. The young insect hatched from one 

 of these eggs is a characteristic larva (Fig. 47 d), strikingly 

 unlike its parent, the body flattened in form with indistinct 

 segmentation and an oval margin fringed with bristles, the 

 short legs, with undifferentiated shin and foot segments and 

 no claws, not being visible from above, while the feeler has 

 only three segments. This tiny larva only about a quarter 

 the length of its parent moves actively about and feeds until 

 the time arrives for the first moult ; this is brought about, 

 after preliminary up-and-down movements of the abdomen, 

 by a splitting of the cuticle at the front edge so that the insect 

 gradually works its way out, the old cuticle slipping off back- 

 wards. The second-stage larva (Fig. 47 e) is of the same 

 general form as the first, but the legs are very short and rudi- 

 mentary so that the creature becomes sluggish in its behaviour 

 a condition which persists into the third stage, like the second 

 but larger the insect being now half as long as the adult. 

 Throughout the larval stages no trace of wing-rudiments is 

 apparent. The final larval instar (third or fourth) after a 

 short period of feeding settles down on a leaf to which its 

 body-margin is closely applied, and the cuticle separates from 

 the underlying skin without being shed. Wing-rudiments 

 then grow out from the second and third thoracic segments ; 



