12 BRITISH INSECTS 



functionless until the cuticle has been cast for the last 

 time. Indeed, until the final or adult stage of the 

 life-history is reached, the wing-rudiments lie within 

 pockets of the chitinous outer crust. Higher in the 

 scale of insect life we find still more striking meta- 

 morphoses. The uninitiated would fail to connect 

 the sluggish, mud-coloured young of the dragon-fly 

 with the alert and resplendent winged being by which 

 it was begotten. Highest of all, we find such insects as 

 butterflies, bees, and two-winged flies, which begin life 

 as a hungry caterpillar, grub, or maggot, pass through 

 a period of quiescence when no food is taken, and 

 then undergo a final moult before reaching sexual 

 maturity. In these last-named cases the wing-rudi- 

 ments lie hidden within little pockets or in-pushings 

 of the true skin or epidermis until the quiescent stage 

 of development is reached ; but at the period of the 

 penultimate, or last-but-one, moult, they are withdrawn, 

 and at its conclusion are plainly visible beneath the 

 newly-formed cuticle or exoskeleton. 



Several convenient terms are used to describe 

 insects in different stages of their metamorphoses. 

 When there is no quiescent period, the creature is 

 usually referred to as a nymph from the time when it 

 leaves the egg until it becomes adult. But when the 

 life-history, subsequent to hatching, exhibits three 

 strongly contrasted stages, the insect is known first 

 as a larva, then as a pupa, and finally as an imago, or 

 adult. The term " larva," which is applied to any 

 young animal that differs markedly from its parents, 

 is in practice often discarded in favour of a more 

 expressive substitute. Thus, when the larva is soft 

 and cylindrical, with pairs of short, stumpy " prolegs " 

 on certain of its hinder segments, it may properly be 



