332 Proceedings of the Royal Society of Edinburgh. [Sess. 
made only by frequent and continued examination of an infected area, and 
in any case will always be difficult. The adult is small, and, except on 
close examination, is readily confused with the numerous Hymenoptera 
which are to be seen on a summer’s day. 
So far as the insects inhabiting the Scots pine stumps are concerned, 
Hylobius abietis appears to be the only one which Bracon attacks. In 
all cases where its cocoons were collected they were invariably accompanied 
by the head of the grub of Hylobius. Observations also show that freshly 
felled stumps, stumps less than one year cut, may harbour Hylobius grubs, 
but that it is in the second year of felling that Bracon cocoons are first to 
be found. The Bracon persists as long as the weevil larvae, and fresh 
unopened cocoons may be found when no weevil larvae are present, 
indicating that Bracon has accounted for them. 
On the whole, Bracon is extremely hardy, and can endure similar 
conditions to its host. 
The Distribution of Bracon sp. 
Two methods of determining the distribution of the Bracon have been 
adopted. Suitable areas have been examined personally, and pieces of 
roots known to contain Hylobius grubs have been obtained from areas 
which were not readily accessible. Through the courtesy of the Board of 
Agriculture for Scotland a memorandum was sent to landowners and 
foresters throughout the country asking them to send in roots for examina- 
tion from suitable areas. The following is a list of the counties in which 
the Bracon has been found to occur in Scotland : — 
Aberdeenshire. 
Elgin and Moray. 
Fifeshire. 
Kincardineshire. 
Midlothian. 
Nairn. 
Peebles. 
Renfrew. 
Boss-shire. 
This list is of course incomplete, but it indicates a wide and prob- 
ably general distribution of Bracon. It is probably present wherever 
Hylobius abietis occurs in numbers. 
It is certain that the Bracon is no inconsiderable factor in helping 
to keep the numbers of H. abietis in check. This useful work might, 
be supplemented by the experimental introduction to an area infested 
with Hylobius of additional numbers of Bracon. Laboratory experi- 
ments show that the Bracon can be reared in large numbers during the 
summer. 
