THE HIDDEN TYPE OF WING-GROWTH 109 



segments, the foot, not distinct from the shin, carrying a strong 

 claw. The prothorax and the first eight abdominal segments 

 have each a pair of laterally-placed spiracles ; on each side 

 of the ninth abdominal segment is a large dark oval depression 

 which looks like a spiracle but is really an ingrowth of the 

 cuticle for the attachment of muscles. This ninth segment 

 ' among the commonest wireworms (larvae of Agriotes] ends in a 

 sharp conical point, but in some members of the family (Athous 

 for example) its extremity is broad and bifid. Below it the 

 tail-segment (" anal proleg ", see p. 101) projects downwards. 

 The wireworm is admirably adapted for working its way 

 through the soil ; with its wormlike shape and the marked 

 shortening of its legs and feelers, it presents a striking contrast 

 in form to its parent-beetle. 



Another well-known beetle-grub of somewhat the same 

 general aspect as a wireworm is a " mealworm " such as the 

 larva of Tenebrio, not infrequently found living and feeding 

 in flour and other food-stuffs. This has an elongate sub-cylin- 

 drical body similar to that of the wireworm, the head being 

 more rounded, the feelers a little longer, and the legs more 

 conspicuous. The cuticle, though firm, is thinner than that of 

 the wireworm, and the ninth abdominal segment ends in two 

 prominent, upturned, dark points. Both mealworm and wire- 

 worm display after each moult a new cuticle, pale and whitish 

 in aspect ; this becomes darker in colour as it hardens and 

 increases in thickness. 



The wireworm and the mealworm retain the hard exo- 

 skeleton of the campodeiform type of larva but differ in their 

 wormlike aspect and their short limbs. In many other 

 beetle grubs we find modifications in other directions : the 

 general shape of the campodeiform larva is preserved and the 

 legs remain relatively long, but a large part of the cuti- 

 cular area is comparatively thin and flexible, a number of 

 hard, thickened plates or tubercles on which stiff bristles or 

 spines are arranged, forming an incomplete, but probably 

 efficient protective armour. Thus in such a larva as that of 

 one of our common " ladybirds " (Coccinella] beetles easily 

 recognized by their rotund form, apparently three-segmented 

 feet, and conspicuously spotted colour-pattern the small 

 head-capsule is firmly chitinized, while the cuticle over most 



