172 THE BIOLOGY OF INSECTS 



a twig or even a leaf-edge of its food-plant. The body- 

 segments are still all much alike, the cuticle is usually thin 

 and flexible, and the general aspect of the caterpillar may be 

 described as worm-like ; it is essentially a " creeping 

 thing." 



The newly hatched caterpillar is very small, but it feeds 

 voraciously and grows quickly, passing through its successive 

 stages and undergoing four or five moults before it attains 

 its full size. The caterpillar in its last stage is enormous 

 compared with what it was when it left the egg, but it does 

 not differ in any essential feature of outward form. Head, 

 body-segments, jaws, legs, and pro-legs appear after each 

 moult much as they did before it, and at no stage of larval 

 life is there any trace of outward wing- rudiments. This 

 last feature is, as D. Sharp (1898) pointed out, by far the 

 most important of the readily observable distinctive cha- 

 racters of the type of life-history illustrated by the trans- 

 formation of the caterpillar into the butterfly ; we have 

 seen that in the growth of cockroaches, bugs, aphids, and 

 cicads, there are evident wing-rudiments at an early stage 

 of growth after hatching, and the same condition is found in 

 the aquatic nymphs of stone-flies, may-flies, and dragon-flies. 

 But in the development of the butterfly no trace of wings 

 is apparent until the last larval cuticle has been shed and 

 the pupa revealed ; on the pupa (Fig. 45, c) the wings may 

 readily be seen at either side of the body, so closely 

 adpressed indeed that they do not stand out, but quite 

 recognisable as to their shape, as are also the legs and 

 feelers, elongate like those of the adult, and sometimes also 

 the slender, flexible maxillae which will enable the butterfly 

 to feed by suction, the biting mandibles of the caterpillar 

 used for feeding on solid plant tissues having vanished. 



The pupa, then, resembles the adult insect much more 

 closely than the larva, and this can be seen more clearly 

 than in the case of the butterfly if we study the pupa of a 

 beetle (Fig. 47, b) or a bee. For in these insects the pupal 

 wings and legs are not closely adherent to the body as in the 

 '* obtect " butterfly chrysalid, but stand out in the manner 



