56 INSECT TRANSFORMATION 



in which the legs of the front pair are greatly reduced, the 

 short shins clothed with delicate scales giving the appearance 

 of fine brushes, and the feet being suppressed. 



The internal organs (Fig. 30 C) of the butterfly or moth 

 also display some important modifications. As the jaws are 

 adapted for taking liquid and not solid food, the gullet in the 

 head-region is expanded to form a sub-globular sac, whose 

 walls, capable of contraction and dilatation through the action 

 of appropriate muscles, serve to suck in the fluid nourishment 

 through the trunk. Further, the crop instead of being placed 

 directly between gullet and stomach is a blind, bladder-like 

 side-outgrowth (Fig. 30 C c) of the former and a somewhat 

 similar blind outgrowth of the hind-gut forms a rectal caecum 

 (r c). As no solid food is swallowed there is no gizzard, 

 mastication and straining of particles not being required. 

 The excretory tubes, very numerous in the grasshopper, are 

 only four in number in the butterfly. 



In the central nervous system a noteworthy specialization 

 is seen in the close approximation of the second and third 

 thoracic ganglia which appear to form a single large nerve- 

 centre (Fig. 30 C, ii, iii) situated in the mesothorax, and the 

 prothoracic ganglion (i) lies immediately in front. Such a 

 marked centralization of portions of the ventral nerve-cord is 

 carried to a still further stage in other highly-organized insects. 

 The chain of abdominal ganglia retains in the moth or butter- 

 fly much the same extended arrangement that it has in the 

 grasshopper, but here also there is often condensation, only 

 four or five distinct centres being recognizable (Fig. 30 C). 



From the egg, laid by the female butterfly or moth on a 

 leaf of some suitable food-plant, is hatched the characteristic 

 larva familiar as a caterpillar (Fig. 29 bed). The caterpillar has 

 a worm-like cylindrical body, most of the area of the cuticle 

 being thin and flexible, so that the creature is comparatively 

 soft, though on each segment there is a regular series of bristle- 

 bearing tubercles, and when the bristles are very strongly 

 developed, the caterpillar becomes markedly spiny or hairy. 



The head-capsule (Fig. 31 C) is hard and firm, the cuticle 

 being thick and compact, and a comparison of the caterpillar's 

 head with that of the adult insect is instructive. In place of 

 the butterfly's large compound eyes, the caterpillar has a 



