Beetles 



283 



The eggs are usually laid on the bark, and the whitish, usually footless, 

 soft-bodied but hard-headed and strong-jawed larvae burrow about in the 

 tree-trunk for a year or two or even three (varying with the different species), 

 feeding on the chewed wood. They pupate in the burrow, in a cell par- 

 titioned off with chips, or sometimes specially made just under the bark. 

 The beetle has only to gnaw its way through the bark or the loosely plugged 

 burrow to escape from the tree. These wood-borers usually select a 

 weakened or dying tree for attack. 



The largest Cerambycids belong to the subfamily Prionidae (Fig. 392), 

 whose members have the sides of the prothorax sharply margined and 

 usually toothed. Prionus laticollis, the broad-necked Prionus, varies from 



FIG. 394. The sugar-maple borer, Plagionotus speciosus, larvae and adult beetle. (After 



Felt; natural size.) 



i inch to 2 inches in length, and is pitchy black or brown, the prothorax 

 with three sharp teeth on each lateral margin, and the antennas i2-segmented; 

 the larvae, which live three years, are great footless white grubs, 2^ to 3 

 inches long, which burrow in the roots of oak, poplar, cherry, apple, 

 grape-vine, and blackberries. The tile-horned Prionus, P. imbricornis, 

 a similar beetle, has nineteen antennal segments in the male and usually 

 sixteen in the female; Orthosoma brunnea, is long (ij to 2^ inches) and 



