The Ecology of a Sheltered Clay Bank 163 
the piles of sawdust here and there on the ground, this 
work must have been going on for a good many days. 
Hence the emergence of the bees was simultaneous, but 
whether from hibernation or from the pupal stage I do 
not know, since I could not ascertain just how this species 
spends the winter, unless I used an ax on the rafters, 
and this I had not the immoral courage to do. However, 
it was plain from the first that no new tunnels were being 
made, but that old ones were being enlarged. 
The activities of the bees in tunneling and pollen-gath- 
ering increased, although not their number, up to July 
16, when they almost completely disappeared. This was 
probably the end of the first generation of 1917, regard- 
less of whether they had hibernated or had emerged as 
new adults in the spring. 
On July 30, other adults appeared—probably the first 
of the second generation. On this first day, two females 
were at work; on the next day four were in evidence, 
and the numbers continued to increase during the next 
few days, until by August 20 they were more abundant 
and seemed more industrious than the population earlier 
in the season. They were so intensely busy cutting out 
the tunnels, and they threw down the yellow dust to the 
ground in such abundance that the pits of the ant-lion 
larvae beneath suffered complete obliteration. They 
were seen in the same activity and numbers up to Sep- 
tember 7 (with certain pauses in their work due to mete- 
orological conditions described elsewhere). The three 
nights before September 12 were very cold; the insects 
about the unit were dwindling in numbers, and those 
which still lived were slow to come out of their burrows. 
That day it was 2 o0’clock in the afternoon before the first 
carpenter bee made its appearance, but her sisters re- 
