102 



FOREST ENTOMOLOGY. 



rough bark, or on old standing trees which are considerably past their 

 best. It often happens with trees of the latter character that one 

 side of the stem presents bark harder and more nearly dead than the 

 other, and the beetles should be looked for on the less vigorous side. 

 The presence of a few exit-holes will often assist in revealing the 

 abode of this species. 



The life-history of this species is not quite so clear as one would 

 wish. In some cases the generation is said to be double-brooded, 



whilst in other cases there 

 are two generations in three 

 years. The flight period is 

 about the beginning of April, 

 or about the middle of Oc- 

 tober. The female makes a 

 short, bent, and deep gallery, 

 which is, as a rule, double- 

 armed, but single-armed gal- 

 leries are often found. 



As a rule, the larvae have 

 no decided method of mak- 

 ing galleries, and it is there- 

 fore very difficult to accept 

 any particular markings as 

 typical. This difficulty is 

 intensified by their boring 

 habits, inasmuch as you 

 may find them either in the 

 deep bark or in the wood 

 itself ; therefore when the 

 bark is removed the markings found on the wood are often only part 

 of the workings. When, however, we do find the extreme length 

 of the workings, they are generally about 6 inches long, and often at 

 right angles to the mother-gallery. In consequence of the extreme 

 length of the galleries, much harm may be done to very old trees, 

 as these galleries may encircle the stem, and thus hasten decay. 

 Fig. 93 is a representation of the markings of this insect. 



The beetle (fig. 94) is about 4 to 5 mm. in length, of a convex form, 

 pitchy black throughout, somewhat shiny, and with comparatively long 

 antennae. The latter are often ferruginous in colour, with the shaft 



Fig. 93. Ml 



rkings o/Hylesinus crenatus on ash stem 

 after removal of bark. 



