THE METAMORPHOSIS OF INSECTS 



185 



prolegs are wanting. This type is quite characteristic of the larvag 

 of the Scarabasidag, hence the name ; but it occurs in other groups 



of insects. 



The movements of these larvae are 



slow; most of them live in the ground, 



or in wood, or in decaying animal or 



vegetable matter. 



Fig. 204. — Larva of Melolontha 

 vulgaris (After Schiodte). 



Vermiform. — Those lar\^ce that are 



more or less worm-like in form are 



termed vermiform. The most striking 



features of this type are the elongated 



form of the body and an absence of 



locomotive appendages (Fig. 205). 



Naupliiform. — The term naupliiform is applied to the first instar 



of the larv^a of Platygaster (Fig. 206), on account of its 



resemblance to the nauplius of certain Crustacea. 



The prepupa. — Usually the existence of an instar 

 between the last larval one and the pupal instar is not 

 recognized. But such a form exists; and the recogni- 

 tion of it becomes important when a careful study is 

 made of the development of holometabolous insects. 

 As is shown later, during larval life the develop- 

 ment of the wings is going on within the body. As 

 the larva approaches maturity, the wings reach an 

 advanced stage of development within sac-like invagi- 

 nations of the body-wall. Near the close of the last 

 larval stadium the insect makes preparation for the 

 change to the pupa state. Some form a cell within 

 which the pupa state is passed, the larvae of butter- 

 flies suspend themselves, and most larvae of moths spin 

 a cocoon. Then follows a period of apparent rest before 

 the last larval skm is shed and the pupal state assumed. 

 But this period is far from being a quiet one; within 

 the apparently motionless body important changes 

 take place. The most easily observed of these 

 changes is a change in the position of the wings. 

 Kach of these passes out through the mouth of the sac in which it has 

 been developed, and lies outside of the newly developed pupal cuti- 

 cula, but beneath the last larval cuticula. Then follows a period of 

 variable Hnration in different insects, in which the wings are really 



Fig. 205. 

 Larva of 

 crane-fly. 



