321 
1915-16.] Structure and Life-History of Bracon sp. 
The adults are extremely active, crawling and flying about immediately 
on emergence. They are strongly attracted to light, and if they escape 
from a dark breeding-cage immediately fly to the nearest window. This 
proved a fortunate habit in that on one occasion when three hundred 
escaped all were recovered from the main window of the laboratory. 
Field Experiments. 
Before the value of Bracon as a factor in controlling the Pine Weevil 
could be demonstrated it was necessary to observe it at work in an area 
hitherto free from the parasite. It was found that such areas were not 
common. The experimental area finally chosen was a recent felling on 
Drumshoreland estate, near Edinburgh. It had the following advantages : 
— It was not far distant from Edinburgh, and easily accessible by train. 
The felling was of recent date, and Hylobius larvae were plentiful. At 
the time of selection no Bracon had been found on the area. Later, 
Bracon cocoons were found in a wood near the selected area, and on 
the area itself one batch of fresh cocoons was obtained near the time of 
the experiment. The locality was visited on February 17 and 19, and 
several stumps were examined. These contained several weevil grubs. 
Two methods of introducing the parasite to the area were available : 
to transport the unopened cocoons and distribute them here and there 
over the area; or to set free the adult parasites as they emerged. The 
first method was the easier, but, in view of the fact that nothing was 
known regarding the proportion of the sexes, it was decided to liberate 
the adult parasites after emergence. 
The period during which the parasites were liberated extended from 
May 12 to June 7. They were liberated as follows : — 
Date. 
Males. 
Females. 
Total. 
May 
12, 1915. 
5 
9 
14 
33 
19, 
5 ? 
72 
88 
160 
5 ? 
20, 
33 
27 
7 
34 
33 
21, 
53 
73 
63 
136 
33 
24, 
53 
156 
226 
382 
55 
26, 
55 
23 
25 
48 
5 ? 
28, 
55 
42 
45 
87 
55 
31, 
55 
18 
38 
56 
June 
3, 
55 
34 
14 
48 
)5 
7, 
33 
23 
12 
35 
Total 
473 
527 
1000 
VOL. xxxvi. 
21 
