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 80 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 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 



