1899-1900.] Dr R. Stewart MacDougall on Genus Pissodes. 325 
State entomologist, I received a number of young (three and 
four years old) Scots pines, which had become sickly and had died 
off from insect attack. On examining these I found the beds of 
P. notatus , and therefore enclosed the pines in a sack in order that 
I might get the images when these emerged later on. I left 
Munich on July 20, 1895, bringing with me the pines to Edinburgh, 
and on opening them out on July 23rd I found that a number of 
beetles had issued. With the material thus won I started the experi- 
ments at the Royal Botanic Garden, Edinburgh, in a part of the 
garden very kindly placed at my disposal by Professor Bayley 
Balfour, to whom I am also indebted for some of the pines used. 
Method of Expekiment. 
During my work in Munich I had become acquainted with the 
* sack-method ’ practised by Professor Pauly in his insect-breeding 
experiments. In dealing with bark- or wood-boring insects whose 
development lasts for some months or longer, it is neither con- 
venient nor always possible to make use of entire stems, and yet 
if branches or sections of the trunk be kept for use, there is always 
the drawback of a rapid drying. In a cut piece of stem evapora- 
tion takes place chiefly from the cut surfaces, and to reduce this 
evaporation Pauly recommended the paraffining of the cut ends. 
Both ends of the cut length of stem are dipped several times in 
melted paraffin, which dries as a thin protective skin over the cut 
surfaces. That by this means, in spite of evaporation, moisture 
is retained long enough for the contained insects to complete 
their development, Pauly’s successful breeding experiments with 
Bostrichidae prove. Personally I have also proved its value. 
The paraffined lengths of stem are placed in a sack made of some 
thin material, and the insects to be experimented with are placed 
inside and the sack securely tied. 
I employed this method at the beginning of my experiments 
with notatus in 1895, but soon departed from it, as I saw that hy 
it I could not obtain sure results as to one important part of my 
inquiry — namely, the length of life of notatus in the imago stage. 
Besides, I was desirous of giving as natural conditions as possible, 
and after some thought devised the following plan. 
