The Bronze Birch ' Borer 



67' 



The borer (Figs; 31 and 35), is i sleiider, 

 flattened, footless, creamy white grub about three 

 fourths of an inch long when fully grown. Its 

 small head with dark brown mouth-parts is 

 retracted into the wide, flattened first thoracic 

 segment giving it a flat-headed appearance. The 

 other segments of the body are not so wide, the 

 second and third thoracic being the narrowest. 

 The caudal end of the body ends in two brown, 

 horny, forceps-like processes with bidentate 

 inner margins. It is this slender creature which 

 is responsible for the killing of the trees. It 

 may be found in autumn by cutting Jnto the trees 

 beneath the rusty-colored spots described on page 

 66 as occuring on the bark (Fig. 30 a). These 

 grubs make tortuous or zigzag burrows in the sap- 

 wood around and across the trunk and branches 

 Fie. ■? I . — The Bronze Birch c • £ ^ j , , •tt /- j 



Borer, a, female beet{e ; b, first ^^ mfested trees, as shown m Figs. 36fl, and 32. 



abdominal segments of male from 

 below; c, grub or borer. All 

 enlarged about three and one- 

 half times. (From Bull. 18, U. S. 

 Bureau of Entomology). 



Work of the Insect 

 This borer attacks white birches of all sizes 

 from nursery trees to stately mon^archs more than 

 a quarter of a century old. All parts of the tree, from branches a quarter of 

 an inch in diameter to the main trunk, may be infested. The top branches 

 are always first attacked and killed, then the infestation spreads into the other 

 branches and trunk. 

 The tiny borer, 

 hatching from an egg 

 laid by the adult or 

 beetle on the bark, 

 begins a narrow mine 

 or burrow through 

 the bark. The bur- 

 row is extended in a 

 tortuous or zigzag 

 direction along the 

 branch, getting wider 

 as the borer grows, 

 and running mostly 

 in the sap-wood just 



JiAncQl-V. th« V.-.rlr hnf 1^"5- ^2—The hiirrow oj a single borer as it zigzagged around 

 oeneam me oarK, out ^^^^ through this z-foot branch for a distance of over s feet. 

 sometimes going for a Much reduced. 



short distance deeper into Ihe wood, even to the centre of the branch. The 

 borer packs the burrow behind it with its excrement and wood particles which 



