314 THE BIOLOGY OF INSECTS 



Sub-class III. ENDOPTERYGOTA 



These are winged (or secondarily wingless) insects, 

 developing from larvae that are usually much unlike the 

 adults, with wing-rudiments growing in hidden pouches 

 pushed inwards from the body-wall (Fig. 46), so that they 

 become apparent only in the penultimate stage, which is 

 a true pupa, usually quiescent and taking no food. Many 

 other organs of the adult arise before and during the pupal 

 stage from groups of cells (imaginal discs) present in the 

 larva, so that there may be much reconstruction in the 

 course of development. 



Order 15. COLEOPTERA 



The Beetles have strong biting mandibles, a freely 

 movable prothorax, and the hard, firm forewings modified 

 'into sheaths (elytra) beneath which the membranous hind- 

 wings can be folded when not in use. (In many beetles the 

 hindwings are vestigial or absent.) Beetle larvae vary 

 greatly in form from the active, firm- coated, long-legged 

 campodeiform type to the soft-coated cruciform grub with 

 legs reduced or wanting (Figs. 47, 48, 49). In the growth 

 of some beetles the former type is succeeded by the latter 

 (hypermetamorphosis). The wings and limbs of a beetle 

 pupa (Fig. 47, b) are free from the body. 



Orderi6. NEUROPTERA 



These insects have biting jaws and two pairs of mem- 

 branous net- veined wings usually alike in form. There are 

 no abdominal cercopods. The larvae are usually campodei- 

 form and the pupae free in type. 



Sub-order i. MEGALOPTERA 



The Alder-flies and Snake-flies have the wing- 

 neuration comparatively simple, and their larvae have 

 biting mandibles like those of the adults. 



