ITS OUTER SKELETON. 



49 



closely resemble, but the maxillaa are stunted cylinders formed 

 mainly of simple rings, and very like the antennae. They show, 

 however, the beginnings of three processes (palp, galea, and 

 lacinia), which are usually conspicuous in well-developed maxillae. 

 The second pair of maxilloe (Lni) are coalesced, as usual, and 



Mn 



Fig. 22. Head of larva of Goat Moth, seen from behind. 

 Copied from Lyonnet. 



form the spinneret. The mouth-parts of the Caterpillar do not 

 therefore in all respects represent a universal stage of develop- 

 ment, but show important adaptive modifications. The man- 

 dibles are rapidly pushed forward, and attain their full 

 development in the larva ; the first pair of maxillrc are tempo- 

 rarily arrested in their growth, and persist for a long time in a 

 condition which Orthopterous embryos quickly pass through ; 

 the maxillae of the second pair are not only arrested in their 

 growth, but converted to a special use, which seems to stop all 

 further progress. The labial palps, indeed, which are not at all 

 developed in the caterpillar, survive, and become important 

 parts in the moth ; but the greater part of the labium disappears 

 when the time for spinning the coccoon is over. 



We come next to the Orthopterous mouth, which is well 

 illustrated by the Cockroach. This is retained with little modi- 

 fication in all the biting Insects (Coleoptera and Neuroptera). 

 The mandibles may become long and pointed, as in Staphylinus 

 and other predatory forms ; in some larvoe of strong carnivorous 

 propensities (Ant-lion, Dytiscus* Chrysopa) they are perforate at 



* In Dytiscus the mandibles are perforate at the base, and not at the tip. See 

 Burgess in Proc. Bost. Soc. Nat. Hist., Vol. XXI., p. 223. 



E 



