326 Proceedings of Royal Society of Edinburgh. [sess. 
I used young pines from three to five or six years of age. Each 
pine as it was required was uprooted from the nursery or plantation, 
and after being subjected to careful scrutiny to make sure it was 
quite free from insect attack, it was immediately planted in soil 
in a ‘ pot ’ large enough to conveniently hold it. To surround the 
pines I had sacks made 30 inches high by 60 inches in circumfer- 
ence, or 40 inches by 80 inches, etc., according to the size of the 
pine. The sacks were open at both ends. Over each potted pine 
such a sack was slipped. It was securely tied round the top of the 
‘pot,’ and stakes were inserted into the soil of the ‘pot,’ and on 
these the folds of the sack rested. A counted number of specimens 
of beetle was then placed on the pine, and the sack secured at the 
top. 
The material of which the sacks were composed consisted of 
the very thinnest muslin. So thin was the muslin that the Pissodes 
could be seen from the outside, crawling up on the inside of the 
bag. Each potted and muslined pine was then placed outside in 
the garden, quite exposed to all weathers, and except that the en- 
closed beetles were protected from outside enemies like ichneumon 
flies and birds, their condition may be described as natural. To 
give the pines every chance as regards their health, the pots 
were sunk in the soil up to their rim. 
At certain intervals the sacks were opened for examination, and 
when the proper times came round the beetles were looked for and 
carefully counted previous to their being placed on fresh material. 
This proved a very tedious part of the experiment, as the beetles 
being small, and resembling in a very perfect way the colour of 
the bark of the pine, not to say the soil, much time had often to 
be spent in searching for them. The pines, thus freed of their 
feeding beetles, were once more placed outside, each with its bag 
surrounding it. Now and again, by little dissections, one traced 
the progress of the developing brood, which, as it issued, was 
caught inside the muslin bag. To ensure perfect accuracy, if after 
very careful search the number of beetles previously placed inside 
was not exactly accounted for, dead or alive, the pine was removed 
from its pot and most carefully examined previous to its being 
placed in a new pot, 
