HOMOMORFHA. 



357 



and the Mallophaga alone, in consequence of parasitic life and the 

 loss of the wings, metamorphosis is lost (acquired ametahole, Lang). 



The Insects belonging to this type may be divided into two groups, 

 according to the manner of their metamorphosis. 



1. Paurometabola. The post-embryonic development is accom- 

 plished, through a series of moults, by the gradual growth of the 

 body, of the wing-rudiments and the outer genital apparatus. This 

 growth, though probably continuous, appears to be intermittent, 

 being only visible at each moult. In Insects belonging to this 

 group, the young stages resemble the adult, not only in form, but 

 also in manner of life. 



The Dermaptera, Orthoptera genuina, Corrodentia, Thysanoptera, 

 and most Rhynchota conform to this type. 



Fio. 176. — A, larva. B, pupa. C, imago of Cicada septemdicem (after Packard). 



The young forms of most Rhynchota resemble the imagines in the structure 

 of the mouth-parts and in the shape of the body, and change gradually into the 

 adult form. The genus Aleurodes is an exception ; its shield-shaped larva differs 

 in appearance from the winged imago and passes into a resting, pupal stage, 

 which is covered by the larval integument. There is here therefore complete 

 metamorphosis. The same is the case in the male of the Coccidae, which 

 changes into a resting pupa enclosed either in a protective larval integument 

 or in a spun cocoon. The Cicadidae also (Fig. 176) attain a higher degree of 

 metamorphosis. The larvae (A) live beneath the ground on the roots of trees, 

 and are provided with hook-shaped fore-limbs adapted for digging. The nymph 

 (B) is here capable of movement. Only shortly before the imago hatches does 

 it remain quiet, while waiting for the bursting of the integument. 



