320 Proceedings of the Royal Society of Edinburgh. [Sess. 
flexible, broader at their basal end, and covered with tiny hairs. The 
borer consists of three pieces, the borer proper and two dart-like rods, 
the spiculse. The spiculse lie inside the borer, whose edges overlap them. 
Together the borer and the two spiculse form a tube along which the egg 
passes. These spiculse are barbed at their apices, and are capable of sliding 
up and down in the channel formed by the borer. In oviposition the outer 
sheaths play no part, being raised over the back of the insect. They are 
also slightly raised during pairing. 
Habits of Bracon sp. 
The Larva. 
The host of the larva is, as already mentioned, the grub of the large 
Pine Weevil (. Hylobius abietis). This grub, when full-grown, is a large 
creature measuring 20-25 mm. long. Like all weevil grubs, it has a legless, 
fleshy, curved body, a well-marked brown and strongly chitinised head, 
and strong biting jaws. The whole of its life is spent tunnelling in the 
bark of the Scots pine stump on which it feeds. 
The Braconid larvae, on hatching, crawl all over their host’s body. 
Soon they begin feeding (Plate II, fig. 14). They do not pierce the skin 
of their host, and show no preference for any part of its body, except that 
during their first and second instars they feed in the folds of the body. 
This would seem to be a precaution against falling off or being pushed off 
by the rubbing of their host against its tunnel. Occasionally the parasites 
do fall off, but they soon crawl on to their host again and resume feeding. 
By the time that the Braconid larvae have reached their third moult 
the host has ceased feeding, although apparently still healthy and, though 
quiescent, if roused by the touch of a pencil or twig still capable of action. 
This quiescence begins four to six days after the eggs have been laid. 
During the next day or two the grub becomes flaccid. There is, however, 
not the slightest sign of decay or putrefaction. 
By this time the parasitic larvae are nearly full-grown. Their rate of 
growth is extraordinary. They double their bulk in a day’s time, and 
increase to eight times their original size in from five to six days. They 
may feed for some time at one spot and then for no apparent reason leave 
it and resume elsewhere, yet no trace or sign of puncturing is visible on 
the skin of their host. 
The Adult. 
In emerging from the cocoons the Braconids bite an oval-shaped hole 
in the end of the cocoon. The long axis of this opening lies along the 
length of the cocoon. 
