GROWTH AND TRANSFORMATION 179 



elongate with very short legs adapted for working its way 

 through the soil where it spends its relatively long life of 

 two or three years feeding on roots of plants. A chafer 

 grub (Fig. 48) also feeds on roots, but does not wander as 

 the wireworm does ; only its head and its relatively long 

 legs are firmly chitinised, the cuticle of the body-segments 

 remains pale and flexible, the tail region being somewhat 

 swollen, so that the grub looks like a fat caterpillar without 

 pro-legs. It spends much time resting in an earthen 

 chamber some distance underground feeding on adjacent 

 roots. The larvae of beetles of the " death-watch " group 

 (Anobium, etc.) 

 live and feed in 

 tunnels which 

 they make in 

 wood, or among 

 stored dried 

 food - materials ; 

 they resemble 

 somewhat minia- 

 ture chafer- 

 grubs, but their 

 heads are smaller 

 and their legs 

 much shorter. 

 From these we 

 pass naturally to the larvae of weevils (Curculionidae) and 

 bark-beetles (Scolytidae), Fig. 49, in which the body- 

 cuticle is white, flexible, and wrinkled, while legs are 

 altogether wanting ; such grubs live in concealed situations 

 in the soil, or in plant tissues, mining leaves or timber, 

 or in galleries beneath the bark. These larvae clearly 

 differ from their parent-beetles more than a caterpillar 

 diflFers from a butterfly. 



Other orders of insects show still greater divergence 

 between larva and imago. A wasp or bee-grub (Fig. 50) 

 is legless and pale like a weevil's, but its cuticle is 

 smoother and more delicate and its head much smaller. 



Fig. 49. — Pine Bark-beetle {Dendroctonus hrevi- 

 comis). North America, o, larva (side view) ; 

 6, male. X 9. From J. L. Webb {U.S.D.A. 

 Ent.Bull. 58, 1906). 



