314 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
biological details o£ which concerning B. hylobii accentuate the doubt 
as to the real name of my species. 
Problems Involved. 
The Pine Weevil ( Hylobius abietis), measuring 8-14 mm. (Plate II, 
fig. 12), is the worst insect pest of forestry in this country. It is an enemy 
of newly formed coniferous plantations. The adult weevil alone is harm- 
ful. It attacks newly planted trees, from three to seven years old, during 
its swarming periods, gnawing the tender bark of stem and branch, and 
by reducing or altogether stopping the sap flow causes these young trees 
to wither and die. It prefers conifers, especially larch and Scots pine, but 
on occasion attacks hardwoods such as birch, beech, and oak. 
The damage it can do is enormous. For instance, in a small plantation, 
about thirty acres in extent, in Kincardineshire, not a single young plant was 
left, all being killed by the weevil. In one estate in Perthshire, so serious 
was the damage done by Hylobius that the forester now delays planting 
for four years after felling, in the hope that by that time the weevil will 
no longer be breeding in the area. 
Life-History of Hylobius. 
The female weevil deposits her eggs in or under the bark of the stumps 
of trees which have been recently felled, confining herself to conifers, and 
especially to Scots pine. The larva on hatching bores and feeds in the 
bark until full grown, when it pupates at the end of its tunnel, in a cavity 
cut out in the wood or in the dry bark. The larva, from the nature of 
its feeding-place, does no harm. On emergence the adult attacks the 
young trees in the neighbourhood of the larval feeding-ground. 
Unfortunately, the system of forestry in vogue in this country favours 
the breeding of Hylobius. Whole woods are cut down in one felling, 
thus providing extensive breeding areas for Hylobius. These areas are 
then replanted, and the weevil finds abundant food immediately on emerg- 
ing. Very rarely are efforts made to arrange annual fellings at some 
distance from one another to avoid extensive clearings. For this reason 
the problem of Hylobius is a serious one, and any methods which aid 
in the reduction of the pest are worthy of serious attention. 
Hitherto the methods employed against Hylobius have been entirely 
mechanical, and accordingly biological methods are naturally of interest. 
The object of this paper is to describe the life-history of this Bracon 
species, its distribution and the degree of its parasitism ; and further, to 
discover the best means of using it to control the Pine Weevil. 
