History and Habits of Pityogenes. 63 
ful study of the contents of the larval burrows reveals the 
presence of five exuvil in many burrows. 
The length of the larval burrow varies from eighteen to 
forty-one millimeters, the average being about thirty-one 
millimeters. 
The length of larval life varies with the temperature and 
moisture, but the average for spring conditions is from eigh- 
teen to twenty-five days. 
Pupation occurs in the pupal chamber which lies princi- 
pally in the sapwood. The pupal period under favorable con- 
ditions lasts five or six days, but may be much longer, de- 
pendent upon temperature. 
The young adults on arising from the pupae, feed upon 
the bark and sapwood for a period varying from one week 
to several weeks before emerging. In favorable weather they 
soon make minute ‘“‘ ventilation openings ” through the bark, 
from which they cast out the frass and excreta. 
Males and females occur in equal numbers in the feeding 
burrows, but in the brood chambers each male has from one 
to eight mates, the average being 2.83 females to each male. 
This disproportion in the sexes is doubtless due to the fact 
that many males lose their lives when constructing the en- 
trance gallery and nuptial chamber. At this time they are 
easy prey to predaceous enemies, many are overcome by 
pitch, and many more are doubtless washed from their bur- 
rows by rain. The females, on the contrary, may pass di- 
rectly from their larval host, in which they remain longer 
than the males, to the already completed nuptial chamber. 
From one and a half to two and a half generations of 
P. hopkinsi are completed each year. Over-wintered adults 
emerge in April or early in May and attack new hosts. Their 
offspring emerge in July and do likewise, while some adults 
of the second generation, if weather conditions are favorable, 
emerge in September and give rise to a partial third genera- 
tion, which passes the succeeding winter as larvae and emerge 
about June Ist of the following spring. 
Study of the engravings reveal several interesting facts. 
The egg galleries vary greatly in length, the longest observed 
