30 



[NSECTS AFFECTING THE APPLE. 



bores upwards and outwards to the bark, lining a 

 cavity at the end of its burrow with dust-like cast- 

 ings, and there rests until spring, when it changes to 

 the dormant chrysalis state (b). The adult beetle 

 emerges from the chrysalis about a fortnight later, 



CL O 



Fig. 9. Round-Headed Apple-tree Borer : a, larva; 6, pupa; c, beetle, 



cats a hole through the bark with its strong jaws, 

 and comes forth to continue the propagation of the 

 species. Thus three years are required for the de- 

 velopment of the insect. 



The place where the larva enters may frequently 

 be detected, especially in young trees, by the sawdust- 

 like castings that are pushed out. The eggs also 

 may often be seen, ami are easily destroyed by press- 

 ing on the bark surrounding them with a knife-blade 

 or some similar instrument. The presence of the 

 larva is shown later by the discoloration of the bark 

 where it is at work. 



The full grown grub, or larva, of the Round- 

 headed Borer, is illustrated at a, Fig. 9. It is about 



