28 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



soon become confused and ultimately form a large cavity gnawed 

 in the bark. Later on, however, they may emerge again to end 

 in well-defined pupating pits or chambers. 



Habits. — H. atniailarius is essentially a soil-dweller, breeding 

 in spruce roots just below the soil level. It prefers roots from 

 half an inch to two inches in diameter, but also breeds on 

 larger and smaller roots. 



Its "feeding" ground, which is distinct from its breeding 

 ground, is the young coniferous plantation. Here, if the beetles 

 are newly emerged and sexually immature, they feed to develop 

 their reproductive faculties ("reifungs-frass") or, if mature, to 

 recuperate after their first breeding period ("erniihrungs-frass"). 

 It is this "feeding," or "frass," which makes H. cimicularius 

 the enemy of the forester. It attacks young, recently-planted 

 conifers just below the root-collar, gnawing away the bark, 

 girdling the root-stem, and by preventing the sap-flow causes 

 the young trees to wilt and die. 



Figure 3 shows the lower portion of a young (four-year-old) 

 Scots pine destroyed by the adult cunicularius. On the plant 

 from which Fig. 3 was made five H. cunicularius and two H. ater 

 were feeding. The gnawed portions of the young plant are 

 unshaded in the figure. 



Often H. cunicularius is accompanied by the large pine 

 weevil, Hylobius abietis, L., which gnaws the bark of the young 

 plant above ground. In fact, so common is this association of 

 II. cunicularius and the weevil that, until recently, I was 

 inclined to consider the Scolytid was a follower of the weevil, 

 which is much the more common beetle and is, in fact, our 

 worst forest pest. That H. cunicularius is, however, primarily 

 destructive I have now abundant evidence. 



Relations to the Forest.— The relations of H. cunicularius 

 to the forest can, I think, best be illustrated by the description 

 of an attack by it. 



On 7th October 19 15, on Darnhall Estate, Peeblesshire, I 

 observed Hylastes damage in a young plantation of Scots 

 pine, larch and spruce, and obtained H. ater and H. 

 cunicularius at work. Adjoining this plantation a small area 

 of woodland, consisting of spruce and Scots pine, in which 

 the spruce predominated, had been and was still being felled. 

 During the spring of 1916, this smaller area was planted up 

 with four-year-old plants of Scots pine, larch and spruce. 



