The Genus Hylastes, Er. | 145 
Of the third class of insects inhabiting the galleries of Hylastes ater the 
chief belong to the Diptera, Families Sciaridee and Mycetophilide. I have 
never reared these flies, and, as I have found them only in the larval state, 
I am unable to give the genera or species. 
LIFE-HISTORY OF H. PALLIATUS. 
Except for its habitat, H. pallcatus does not differ in any remarkable 
way from H. ater as regards life-history. The mother-gallery is cut in the 
same manner, the eggs are laid in the same manner except that in some 
cases niches are cut for them, the hatching of the larve, etc., are all quite 
similar, so that to describe all these phenomena would involve tedious 
repetition. Accordingly, I propose to restrict myself to a short account of 
my laboratory experiments, followed by a summary of my field observations 
on Hylastes palliatus. 
Laboratory Observations on H. palliatus. 
These were begun on 2nd May 1916, when forty adult H. palliatus, the 
females of which were, I believe, proceeding to their first egg laying, were 
introduced into three breeding-cages, each containing two stems of Scots 
pine 2 feet long. From time to time these logs were examined, as in the 
experiment with Hylastes ater. Observations were made on the cutting of 
the gallery by H. palliatus, as in the case of H. ater, and, in view of the 
fact that no remarkable differences in the breeding habits of the two species 
were observed, it is hoped that the following summary of laboratory observa- 
tions may suffice as a description of the life-history. 
fgg laying and Cutting of the Brood-Gallery. 
This period extends from three to four weeks (4th May-30th May) 
in spring, and six to seven weeks in early autumn (17th July—7th 
September). 
Hatching of the Egg.—The duration of the egg stage is four to six days 
(8th May-12th May, 12th May-18th May). 
Duration of the Larval Stage—This extends from eighteen to twenty 
days in the summer or spring brood (12th May-17th June). 
Duration of Pupal Stage-—This lasts from twelve to twenty days 
(1st June-29th June). 
Total Period from Egg to Adult.—This extends for from four to six weeks 
(4th May—29th June). 
VOL. XX. N 
