276 



PROTECTION AGAINST INSECTS. 



the beginning of April, and again in October. When pairing 

 takes place late in the spring (May and June) the generation 

 is only single. 



c. Relations to the Forest. 



This beetle attacks the ash almost exclusively, and prefers 

 large trees with fissured bark. The female makes short, 



slightly bent, generally two-armed 

 galleries. The two arms are gene- 

 rally of unequal length and inclined 

 at an acute angle ; sometimes only 

 one is present. The larval burrows 

 run at first upwards or downwards, 

 that is, at right angles to the 

 mother-galleries, gradually curving 

 and becoming horizontal ; they are 

 of great length, and are often 

 abruptly bent on themselves once or 

 twice in their course. Fig. 135 

 shows the appearance of a gallery, 

 in which boring beetles as well as 

 larvae may be distinguished ; the 

 latter so closely packed that their 

 galleries have coalesced. It is, 

 however, hardly typical of the 

 species. If the ? do not lay, they 

 bore simple tunnels, frequently just 

 under the outermost bark, which 

 then generally splits and flakes off 

 over the point of attack. Excep- 

 tionally the beetle has been found 

 in the Russian Chersonese ; the 



Fig. 135. Burrows of H. crena- 



tus, in ash bark. 

 a Entrance-hole. 

 I Mother-galleries. 

 c Beetles excavating galleries. 

 d Boring larvae. 



attacking old oak-trees 



galleries in this case may be three-armed. 



The attacks of this insect may be treated as for H.fraxini. 



C SUBFAMILY SCOLYTINI. 

 Description of Subfamily. 



This sub-family contains a single genus, ticolytiw, the 

 species of which possess a projecting head with a short, broad 



