198 Bionomics of Cryphalus abietis 



So far as my observations in Scotland sliow, C. abielis has not proved 

 of any great forest importance in the sense of having proved destructive 

 to hve trees, but the species must not be overlooked or observation on 

 it neglected. 



A knowledge therefore of its habits as well as the recognition 

 of the presence of the beetle in our woods at the present time is 

 opportune. 



Its favourite breeding places are dead or almost dead trees, twigs and 

 branches, of practically all ages, that have been spoiled or killed by some 

 agency or other such as wind, breakage, etc. The positions most commonly 

 chosen by the parent beetles for tunnelling their brood galleries are around 

 twigs and branches, the female commencing her gallery in the axil of a side 

 branch. No doubt she chooses this position because a good foothold is 

 secured for her while boring the entrance hole of the gallery. Boring 

 gradually round the base of the side branch she cuts the inner bark 

 layers, namely the bast and cambium, leaving only the thin layer of outer 

 bark. Where the twig or branch around which she has excavated her 

 burrow or gallery is a small one it may be completely girdled and isolated 

 from the main branch. Even when the twig or branch is strong and 

 although only partially girdled by one gallery it may be completely 

 girdled and isolated from the main branch or stem by other galleries. 

 Were such workings then to be cut on living twigs and branches it is 

 quite evident that serious damage would be done to trees, for no food 

 material from these isolated portions could pass down to the main stem 

 and roots. 



A point worthy of mention in connection with C. abietis is that it is 

 negatively heliotropic, the parent beetles preferring bushy twigs and 

 branches in shady places unexposed to the sun. For example, the 

 topmost branches of heaps of brushwood lying in the open are not 

 commonly chosen for brood purposes, while the lower branches of such 

 heaps as well as entire heaps in the shade of standing trees may be 

 badly infested. Most likely those branches which are exposed to the 

 sun are too dry for breeding on and this can be a reason why they are 

 not chosen by the parent beetles. 



To ascertain if beetles are present in a wood one has only to examine 

 carefully the axil of a dead twig or branch, when, if beetles are at work, 

 a minute heap of fine bore dust, reddish yellow in colour, will be seen. 

 If a number of beetles have issued a series of minute exit holes may be 

 seen at irregular intervals on the surface of the bark. Frequently one 

 will find on examination of branches whore the majority of the beetles 



