50 THE LIFE-STORY OF INSECTS [CH. 



much alike, while the grubs of beetles of different 

 families diverge widely from one another. A review 

 of a selected series of beetle-larvae will therefore 

 serve well to introduce this branch of the subject. 

 Beetles are as a rule remarkable among insects for 

 the firm consistency of their chitinous cuticle, the 

 various pieces (sclcrites) of which are fitted together 

 with admirable precision. In some families of beetles 

 the larva also is furnished with a complete chitinous 

 armour, the sclerites, both dorsal and ventral, of the 

 successive body-segments being hard and firm, while 

 the relatively long legs possess well-defined seg- 

 ments and are often spiny. Such a larva is evidently 

 far less unlike its parent beetle than a caterpillar is 

 unlike a butterfly. Perhaps of all beetle larvae, the 

 woodlouse-like grub (fig. 12 b) of a carrion-beetle 

 (Silpha) or of a semi-aquatic dascillid such as He- 

 lodes shows the least amount of difference from the 

 typical adult, on account of the conspicuous jointed 

 feelers. The larval glow-worm, however, is of the 

 same woodlouse-like aspect, and in this case, where 

 the female never acquires wings, but becomes mature 

 in a form which does not differ markedly from that 

 of the larva, the exceptional resemblance is closer 

 still. In all beetle-grubs the legs are simplified, 

 there being only one segment (a combined shin and 

 foot) below the knee-joint, whereas in the adult there 

 is a shin followed by five, four, or at least three 



