171 



THE STRUCTURE, BIONOMICS AND FOREST 

 IMPORTANCE OF CRYPHALUS ABIETIS RATZ. 



By WALTER RITCHIE, B.Sc, B.Sc. (Agr.), 

 Carnegie Research Scholar in Entomology, University of Edinburgh. 



Amongst systematists who have worked on the Scolytid or bark-boring 

 beetles there are great differences of opinion as to the limits of the 

 genus Cryphalus. Following Fowler ^ the genus comprises 24 different 

 species which are widely distributed throughout the world. In his 

 Coleoptera of the British Isles he records six different species some of 

 them amongst the smallest of our indigenous beetles. All of them are 

 of economic importance in forestry. Of our native species two, 

 Cryphalus ahietis Ratz. and Cryphalus ficeae Ratz., choose as their hosts 

 coniferous trees; the others are found on broad-leaved species. 



Till quite recently these two coniferous species were considered rare 

 in Britain but the increasing number oi records of C. ahietis in Scotland 

 makes it no longer possible to describe this beetle as rare. 



In view of new schemes of afforestation it is urgent that we should 

 have exact information on the relative forest importance of the various 

 insect enemies of trees. Further, for purposes of intelligent control a 

 knowledge of the species in its various stages and of its life-history and 

 habits is necessary. With these principles in view the following research 

 on C. ahietis was undertaken. 



The research is based on an investigation of its life-history and habits, 

 carried out by means of observations and control experiments, conducted 

 in the open at Aboyne, Aberdeenshire, and Banchorv-Devenick, 

 Kincardineshire, and of a series of anatomical studies and breeding 

 experiments made in the laboratory at Edinburgh University on and 

 with material collected in the woods in the vicinity of the places named 

 above and in the neighbourhood of Edinburgh. 



Following Fowler the genus Cryphalus possesses the following 

 characters: (1) eyes entire or slightly emarginate, (2) antennae with 

 the sutures of the club distinctly marked, the club itself being somewhat 

 variable in shape, (3) thorax tuberculate in front, margined at base, 



^ Fowler's Coleoptera of the British Isles, v, 428-430. 



