106 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



the identity of gallery-system may in such cases be established by 

 examination of the beetles. I have not been able to find a con- 

 stant difference between the gallery-systems of the two species. 



The host plants on which I have found both species were 

 Scots pine. In those trees which had been felled or blown, 

 but which still retained the withered needles, the insects were 

 common. They were also common on branches that had been 

 cut off the trees and had been lying on the ground for about a 

 year. I have not found either species in young living trees, 

 even in cases where young plantations adjoined blown areas 

 and the beetles were common. Numerous cases have been 

 recorded from Continental forests in which the bidentatus species 

 had destroyed large areas of young pine, and there are also 

 records of attacks on spruce. Attack on spruce only takes 

 place when pine is not available. The genus Pityogenes has 

 been classed as very dangerous by some authorities; how are we 

 to regard it in our country ? It might be argued that inter- 

 ference in existing conditions is not desirable or necessary. 

 It is a sound principle to inflict loss on an enemy whenever 

 opportunity presents itself, and the principle may be well 

 extended to dealings with this doubtful neutral. Clean wood- 

 lands are desirable, and destruction of brushwood, if it removes 

 food, removes also the beetles that feed on it. 



Points of General Interest connected with the Genus. 



In connection with breeding experiments which were com- 

 menced, it was necessary to collect adult beetles as they 

 emerged from the galleries. It has been noted above that 

 the number of females working from one copulating chamber 

 may be as high as seven. The number of males emerging, 

 in a new brood, was found to be about half that of the 

 emerging females, which is at all events about double 

 the number necessary. Does this fact show only another 

 provision against possible accidents to the male during the 

 period in which he seeks a suitable position for fresh breeding- 

 place, or is it possible that two or more males may live in one 

 gallery-system ? I have not found on any occasion two males 

 in a freshly-formed gallery-system. 



I wish to thank Dr R. Stewart MacDougall for his kind- 

 ness in lending books and material, and for his supervision 

 of my observations. 



