274 



PROTECTION AGAINST INSECTS. 



c. Relations to the Forest. 



The beetle bores into the bast of ash-poles and trees, 

 constructing extremely regular, double-armed, horizontal 

 galleries, with a short entrance-burrow (Fig. 133, a). The 

 larval galleries are short but close together, cutting deeply 

 into the wood, and are always very regular (Fig. 133, b). The 

 pupal chambers are in the wood (Fig. 133, c). The beetles eat 

 their way out in August, making numerous perforations, so 

 that the bark is riddled, as if by shot. Once a tree has been 



Fig. 133. Burrows of H.fraxini, Fabr., on ash sapwood. (Natural size.) 

 a Mother-galleries, b Larval galleries, c Pupal chambers. 



attacked, numerous galleries are excavated in it one over 

 the other. 



The beetle prefers quite sound trees, according to Hess, and 

 kills them, but Miss Ormerod says that the damage is chiefly 

 done to decayed or sickly trees. This insect also attacks large 

 ash-trees standing in the open, boring down to the bast in order 

 to hibernate there, and such winter-quarters are generally 

 occupied again in the succeeding autumn by more numerous 

 beetles, so that rough, scabrous, rosette-like prominences are 

 eventually formed on the bark. It has occasionally been 

 observed to attack the robinia and apple-trees, but its galleries 

 are then vertical rather than horizontal. It may be laid down 

 as a general rule that the smaller the branches which are 



