GROWTH AND TRANSFORMATION 171 



are very short and inconspicuous, the compound eyes are 

 replaced by a few ocelli, and the maxillae have very short 

 palps and reduced lobes, but the labium though small has 

 its central ligula drawn out into a spinneret whence the 

 silken thread formed as a secretion of the specialised salivary 

 or silk glands, is passed out. The three segments behind 

 the head obviously make up the thorax of a typical insect, 

 as each carries a pair of jointed legs ; yet the caterpillar's 

 leg is very short compared with that of the butterfly, its 

 foot-segments are undifferentiated and it has only one claw 



Fig. 45. — a, Dorsal, and 6, lateral view of Caterpillar of Diamond- 

 back Moth (P/wfe/Za crwa/erarww) ; c, pupa (ventral view). X 6. From 

 Carpenter (journ. Dept. Agr. Ireland, I). 



The abdomen of the caterpillar is composed of the ten 

 segments usually recognisable in the hind body of an insect. 

 In most caterpillars five of these (the third, fourth, fifth, 

 sixth, and tenth) carry each a pair of short cylindrical pro- 

 legs armed with circles or crescents of spines ; these pro- 

 legs are of value in regard to the caterpillar's special mode 

 of life, as they enable the creature to cling to or crawl along 



