LIFE HISTORY 
43 
however, was with 200 flies captured in February fly¬ 
ing about in the sculleries and kitchens of one of the 
colleges at Cambridge. They were quite as active as 
in the summer. The kitchens are underground, and 
the fires are kept up continuously. The temperature 
varied from 65° F. in the mornings to 8o° F. in the 
evenings, and the flies, although somewhat sluggish 
in the morning, became active when the fires were 
poked up. The 200 flies under experimentation were 
transferred to a greenhouse, which was kept in a sim¬ 
ilar temperature to the kitchens where they were cap¬ 
tured, and were kept in closed vessels with a supply 
of moist bread beginning to ferment. It is worthy of 
note, by the way, that he found that on several occa¬ 
sions the flies would not lay their eggs upon bread 
which had not begun to ferment. After the flies had 
been confined twenty-four hours they laid their eggs, 
and on the following day all of the eggs hatched. As 
the bread became moldy the larvae avoided it, and were 
transferred to other enclosures and fed upon stale bread 
slightly moistened. They fed until full grown, then 
crawled away from the moisture and transformed to 
pupae under pieces of newspaper. At a temperature 
ranging between 65° F. and 75 0 F. in February, the 
entire duration of the life round occupied three weeks. 
It thus appears that under artificial heat conditions 
the typhoid fly, given food for its larvae, will continue 
to breed almost as rapidly as during the summer time. 
Mr. Jepson’s observations on the length of life of 
the adult flies in the winter time further support the 
