THE SOCIAL INSECTS 



young animal which in the less specialized insects is termed 

 a nymph. This differs from the adult chiefly in its smaller 

 size and in its undeveloped wings and reproductive organs. 

 Amongst social insects, this type of metamorphosis occurs 

 among the termites, sometimes called white ants. In other 

 insects, there has been a gradual divergence between the early 

 and adult stages, so that one gets for instance the familiar 

 contrast between the caterpillar and the butterfly. What 

 hatches from the egg is a larva which lacks many of the 

 characteristic features of the adult. It often happens that 

 when the larva develops in a protected situation with a rich 

 source of food it becomes a legless maggot or grub. This is 

 found in the ants, bees and wasps, but the grub is not especi- 

 ally associated with social life, since it is found equally in 

 solitary species. The larval and adult stages are specialized 

 for different functions, the former for feeding and growth, 

 the adult mainly for reproduction. In the simpler insects, the 

 early and adult stages are still sufficiently alike for one to 

 change gradually into the other. In the more complex insects, 

 they have become so unlike that a resting stage, or pupa, is 

 interpolated between them, to allow of extensive reorgani- 

 sation of structure. 



Although it was stated earlier that the number of moults 

 is usually fixed, there are many exceptions. Thus the larva 

 of the carpet beetle can stand weeks or months of starvation. 

 If it is not feeding, it gets smaller at each moult. By a process 

 of alternate starvation and feeding, the American entomolo- 

 gist Wodsedalek got one of these larvae to live for five 

 years, getting first smaller, then larger. This potentiality for 

 variation in the number of moults is of great consequence in 

 the social life of termites, though it is not in them known to 

 be controlled by nutrition. 



