26 A BOOK OF INSECTS 



its own immediate needs. Thus, it is scarcely surprising 

 that the appearance of young insects varies greatly in 

 accordance with their customary surroundings and food- 

 habits. Nevertheless, most young insects can be referred 

 to one of two groups. The first of these comprises 

 nymphs and larva? which, on account of their general 

 resemblance to a lowly insect called Campodea (it is a 

 near relative of the well-known " silver-fish "), are termed 

 campodeiform. Young insects of this pattern have well- 

 developed legs and powerful jaws. They are remarkably 

 active and wide-awake, while their skin is commonly more 

 or less hardened, or chitinised, after the manner of the 

 adult. The immature forms of dragon-flies, may-flies, 

 lacewing-flies, and many beetles are of this kind. They 

 may be contrasted with the larva? of many other beetles, 

 of moths, of flies, and of bees and wasps, which conform 

 more or less closely to a caterpillar-like type. Such larvae 

 are termed eruciform — eruca being the Latin word for 

 caterpillar. They are characterised by their cylindrical, 

 soft-skinned bodies, reduced mouth-parts and feeble legs. 

 Their habits are usually sedentary, and their sense-organs 

 are correspondingly reduced. In extreme cases the larva 

 becomes an inert and footless maggot. 



This division of young insects into two groups, however, 

 cannot be rigidly maintained. Among beetles, for ex- 

 ample, an almost complete transition can be traced from 

 one to the other. Moreover, in a few instances both 

 forms of larva occur in the life-cycle of one species. This 

 is so in the case of the oil beetles — those rather repulsive 

 insects which are often abundant among herbage in the 

 early summer. The newly hatched larva is campodeiform. 

 It lives an active life upon plants and flowers, without 

 feeding, until it manages to spring upon a humble-bee. 

 In this way it is carried to the bee's nest, where it first 



