INSECTA 



401 



It may reasonably be assumed that metamorphosis of the Holo- 

 metabola has arisen through larval and adult specialization going on 

 concurrently but in opposite directions, and it is not surprising to 

 find among the orders composing this group, as for instance in many 

 Coleoptera, larvae which are rather nymph-like in that they are well 

 chitinized and possess well-developed legs, and mouth parts re- 

 sembling those of the adults (Fig. 300 A). 



The forms of larvae vary considerably and indicate to a great extent 



Fig. 300. Types of coleopterous larvae. A, Campodeiform larva of Pterostichus , 

 Carabidae (original). B, Eruciform larva of Melolontha, Scarabaeidae 

 (original). C, Legless larva of Phyllobius urticae, Curculionidae. After Rymer 

 Roberts. 



the degree of metamorphosis passed through. A campodeiform larva 

 (Fig. 300 A) is one strongly resembling certain members of the 

 ametabolous Thysanura and possesses well-developed legs, biting 

 mouth parts, antennae and cerci, e.g. many Coleoptera. An eruci- 

 form larva (Fig. 300 B) is fleshy and thin-skinned, its legs are often 

 in the form of supporting struts rather than organs of active loco- 

 motion, and there are no cerci. Further, pi'olegs are often found on 

 the abdomen, e.g. caterpillars of Lepidoptera and sawflies (Fig. 322). 



BI 26 



