180 



Bionomics of Cryphalus abietis 



the branch round which the burrow is cut happens to be a fairly strong 

 one it may be only partially eaten round. On the other hand, if the 

 branch be weak, as is very often the case, the burrow completely girdles 

 the branch. The length of the gallery varies. When the mother gallery 

 is short it is broader, when long it is usually narrower. On an average 

 the distance between the beginning of the mother gallery and its ter- 

 mination, measured along its course, is about | inch in length, while in 



inch. 



breadth it measures from \ 



10 



Fig. 8. Typical brood galleries of C. abietis on a branch of Silver Fir (Abies pectinata D.C.). 

 Note how the mother gallery is cut round a smaller branch (E.). «.= beginning of 

 mother gallery; 6.=; mother gallery widened in parts through the feeding of the 

 young larvae; c.= larval gallery; c^.= pupal bed; ii\ = base of smaller branch round 

 which mother gallery is cut. 



The larval galleries naturally run almost at right angles to the mother 

 gallery, radiating out from it on all sides. Some of these larval galleries 



