LEPIDOPTERA 



255 



larva is shown in Fig. 187. The prolegs, though not fully formed, 



are rehcs of true abdominal appendages. The eggs of a butterfly 



are laid on a food plant which is characteristic of the species ; they 



hatch into larvae of the first instar. These begin eating and grow 



rapidly, and about four 



ecdyses (the number is y\EAO 



constant for the species) 



take place. The larval 



instars generally differ 



slightly in appearance, as 



well as in size. The last 



larval instar, or prepupa, 



becomes nomadic, and 



goes in search of a place suitable for pupation. It then 



spins silk, which is used either as a mat, from which the 



larva hangs itself by the claspers, or a girdle, by which the 



larva binds itself to a plant stem, or a cocoon like that of the 



silkworm. Next the larval skin is spht and shed, and a new pupal 



Jaws 



Antennae Legs 

 Spinnerets 



Pro- legs 



Fig. 



187. — A caterpillar. — From Sandars, 

 An Insect Book for the Pocket. 



SkuLL 



Forehead 



CLipeus 

 Upper Up 



6 Eyes 



Antenna 

 Jaw 



.Max. paLp 

 Lab. paLp 



1^^ Segment 



Spiracle 



Fore leg 



6 Eyes 

 "Antenna 

 MaxiLlaand M.paLp 

 Lower Lip and Lab. palp. 

 Spinnerets 



Fig. 188. — Head of caterpillar. — From Sandars, A Butterfly Book for the Pocket. 



skin is formed which completely encases the body and hmbs ; 

 there are no breaks in this skin except for the spiracles. Such a 

 completely encased pupa is called obtect. After an apparent rest, 

 during which metamorphosis has been going on, the pupal skin 

 sphts down the middle of the back, and the butterfly crawls out. 

 The wings are at first hmp and small. They are steadily expanded, 

 largely by the inflation of their tracheae with air, until they have 

 about nine times their original area. In the process the wing has 



