REPORTS OF THE SWEDISH FORESTRY RESEARCH INSTITUTE. IOI 



" Insects injurious to spruce and pine cones," where he gives an 

 ingenious numerical method of detecting parasites. Hendrik 

 Hesselman deals with regeneration in the pine heaths of 

 Norrland (introducing his nitrate investigations into this study). 

 Gunnar Schotte deals shortly with the production of the aspen, 

 while Sven Oden deals with the action of lime on sour humus. 



On the whole the articles are mainly good, although in some 

 cases they tend to be slightly wordy. They exhibit a practical 

 striving after a knowledge of the facts that underlie certain 

 forest phenomena. 



13. Species of Pityogenes of Interest in Scottish 

 Woodlands. 



(With Plates.) 



By Jambs Fkaser. B.Sc. 



The beetles of this genus are widely distributed in Scotland, 

 but on account of their small size and relative harmlessness, 

 they have up to the present time attracted very little attention. 

 It is well known that with altered conditions of surroundings, 

 the economic importance of species, hitherto harmless, may 

 increase. At all events, it is well to know our possible enemies, 

 and to give some attention to provisions directed to curtail the 

 possibilities of danger when general schemes have become 

 accomplished facts, for then, in conjunction with other factors, 

 these beetles may become a very real danger. 



Their closest well-known relatives are the pine bark beetle, 

 Myelophilus, and the elm bark beetle, Scolytus. With both of 

 those beetles they have certain characters in common, both as 

 regards structure and habits. The members of all three genera 

 are bark-inhabiting insects; the antennae of all carry large club- 

 like endings, and are similar in general form. The general 

 shape of all three beetles is cylindrical, the tibiae are toothed, 

 the tarsi are terminated by simple claws. 



The two species of Pityogenes which have been described as 

 forest-important are the two-toothed bark-boring beetle, 

 P. bidentatus, Herbst., and the four-toothed bark-boring beetle, 

 P. quadridens, Hartig. These are two valid species, and in each 

 species varieties have been distinguished and named. Varieties 

 have been distinguished according to the nature of the projec- 



