1899-1900.] Dr R. Stewart MacDougall on Genus Pissodes. 335 
No. of 
Pine. 
Length of time 
Notatus on Pine. 
Date of Issue 
of first of 
New Brood. 
Length of Time. 
31 
July lOto July 28, 1897 
Apr. 28, 1898 
Over 9 months. 
37 
July 31 to Aug. 19, ,, 
July 20, „ 
About 1 2 months. 
39 
Aug. 2 to Aug. 1 6, „ 
55 55 55 
55 55 55 
40 
Aug. 9 to Aug. 27, ,, 
55 25 , ,, 
55 55 55 
It is impossible, however, to lay down a hard and fast rule as to 
length of time for development from egg to imago, for I have 
found and been surprised at the great variation shown in rate of 
growth and imago escape where eggs had been laid by the same 
beetles, on the same plant, and within a comparatively short 
interval of time one from the other. The part of the plant the 
eggs are laid in ; the difference in quality of food in different parts 
of the same host plant, so that some larvae will feed in better 
places and others in worse ; the possibilities of overcrowding from 
much egg-laying so that feeding larvae will interfere with one 
another ; all these influence development in one direction or the 
other. 
In illustration of the foregoing, and especially to show that issue 
of adult beetles from a pine may last over a much longer interval 
of time than that represented between the laying of the first and 
the last egg, I subjoin details of imago issue from some of the 
experimental pines. 
Pine 2. 
This pine (a four-year-old one) held in it from 17th April 1896 
till about the middle of June 1896, 16 notatus. The first new 
imago appeared on 24th August 1896 and the last on 7th July 1897. 
On 2nd April 1897 I uprooted this pine, which had been standing 
all winter exposed to the weather. On being examined, the part 
of the pine immediately under the surface of the soil, for a depth 
of 2 inches, showed a number of little round exit holes from which 
adult beetles peeped out. One of them on being touched walked 
