BUTTERFLIES AND MOTHS 141 



size, number, and position. The caterpillar casts its skin re- 

 peatedly, the number of times varying in different species, and, 

 except at the period of moulting, feeds voraciously. The food 

 of caterpillars is very various, and although the majority are 

 probably purely vegetable feeders, they will also feed upon 

 leather, horn, hair, cloth, wool, etc. 



Caterpillars have many foes, being preyed upon by birds, 

 Wasps, and insectivorous animals ; but their most formidable 

 enemies are the ichneumon flies, which pierce their skins, and 

 deposit one or more eggs in each wound. These eggs soon hatch 

 into small maggot-like larvae, which live inside the caterpillar, 

 feeding on the fatty portions of its body, while avoiding any 

 vital organ; when mature they may either emerge from the 

 caterpillar's skin and assume the pupa state outside the dead 

 body of their host, or, should the caterpillar live to enter the 

 pupa state, they may pass through their complete metamorphosis 

 within the body of their host. The caterpillars have various 

 means of defence or concealment from their foes, some closely 

 resembling twigs of the foliage upon which they are feeding ; 

 others by warning colours, eye-spots, and vivid bands of colour 

 deceive their enemies, or by assuming aggressive and threatening 

 attitudes avoid attack, or by being clothed with irritant hairs, 

 or having an unpleasant odour or taste, are immune from 

 molestation. 



When the caterpillar is full grown, and is ready to assume 

 the pupa state, it ceases to eat, its colours become less brilliant, 

 and it seeks a suitable place where undisturbed it may undergo 

 its metamorphosis. While the caterpillars of most butterflies 

 attach themselves by their tails either horizontally or vertically 

 to some plant stem, to change to the pupa stage, the caterpillars 

 of many moths construct a silken cocoon, or excavate a cell in the 

 ground, lined with agglutinated earth and silk. Hairy caterpillars 

 often weave their hairs into their cocoons, while others use frag- 

 ments of moss, leaves, lichens, and wood. The duration of the 

 pupa state varies greatly in different insects, but, except in the 

 case of summer broods of double-brooded insects, when it may 

 last only a few days, it extends over a period of several months, 

 the insect usually passing the winter in this condition. During 

 the pupa stage not only are the external organs of the future 



