BORING INSECTS 63 



a twig or branch. When they outgrow this first 

 branch they migrate to a larger one. They fre« 

 quently girdle a branch by burrowing around its 

 circumference just under the bark. The position 

 of the burrows is indicated by the matted sawdust 

 at their mouths. Pruning affected small limbs is 

 beneficial, on account of the grub's habit of mi- 

 grating. Fumigating with carbon bisulphide and 

 killing with wires also have their value. The 

 larva live two years, spending the second year in 

 the large limbs and trunk. A campaign against 

 them should include one treatment of those parts 

 of the tree in the late summer of two successive 

 years. 



The last group of insects worthy of mention as 

 wood borers is the horn-tail tribe, or wood wasps. 

 The commonest species is the " pigeon tremex." 

 The adult is a large, stocky, wasp-like insect, with 

 two pairs of transparent brownish wings. The 

 body is brown with lighter bands across the ab- 

 domen, at the posterior end of which there are in 

 the female three stout spines, used in depositing 

 the eggs in the bark. The larva is stout and 

 cylindrical, with a small head. The adults 

 emerge in summer and lay soon after. The bur- 

 rows of the grubs and the holes made in the bark 

 by the escaping insects are round, and nearly a 

 quarter of an inch in diameter. The insect does 

 not do great damage on account of the small 



