214 



INSECT TRANSFORMATION 



the " glow-worm ", which is not only wingless, but resembles 

 closely in outward aspect the woodlouse-like larva charac- 

 teristic of her family. 



Most of the vegetable-eating beetles, however, display 

 as is usual in metamorphic insects a larval method of feeding 

 diverse from that of the imago. Reference has already been 

 made (p. no, Fig. 62) to the chafer grubs which live under- 

 ground and feed on roots while the adult beetles devour leaves, 

 and (p. 112, Fig. 63) to the caterpillar-like grubs of leaf -beetles 

 of the " turnip-fly " group which mine in leaves or burrow in 

 the interior of stems of herbaceous plants. Such larvae feeding 

 in these concealed situations have a soft, flexible cuticle over 

 the body-segments with small and feeble bristle-bearing 



a 



FIG. 108. BARK-BEETLE (ScolytllS 



a, dorsal view ; b, side view ; c, pupa (ventral view) ; d, larva (side view), x 20. 

 From Chittenden, U.S. Dept. Agric. Entom. Circ. 29. 



tubercles. The white, legless, fleshy grubs of weevils (p. 114) 

 are all concealed feeders, living underground and eating roots 

 like the larvae of the Vine-weevils (Otiorrhynchus), mining in 

 leaves like the Beech-weevil grub (Orchcstesfagi) whose presence 

 between the leaf-skins gives rise to conspicuous brown blisters, 

 or boring in wood like the larvae of Hylobms abietis, the large 

 Pine-weevil. The whole family of the bark-beetles (Scolytidae) l 

 have legless grubs (Fig. 108 d), with white, wrinkled cuticle, 

 like those of weevils. Boring through the bark of the 

 appropriate food-tree, the female beetle (Fig. 108 a b) eats 

 out a tunnel on the inner aspect of the bark laying eggs along 

 it on either side at regular intervals. The larvae, when hatched, 

 burrow along lateral tunnels opening out from the mother- 



1 W. Eichhoff : " Die europaischen Borkenkafer ". Berlin, iSSi. 

 A. T. Gillanders : " Forest Entomology ". Edinburgh, 1908. 



