No. 641] 



THE DURATION OF LIFE 



485 



ference of 10° C. The averages were much lower than 

 those found by Hyde and Lutz because, of course, of the 

 inadequate food. At 19° C. the culture in water had an 

 average duration of life of 4.1 days and those in 1 per cent, 

 cane sugar of 12.3 days. In 1917 the experiments were 

 repeated, using sterile flies on 2 per cent, glucose agar 

 which was found to be a more adequate food. Similar 

 results were obtained, getting a simihxr coofHcient for the 

 duration of the larval and pupa stages, and finding that 

 the ratios of the duration of the three different stages re- 

 mained approximately constant for the different tem- 

 peratures. The averages here of the life of the imago 

 are more of the order of those found by previous workers, 

 228 flies at 30° lived an average of 13.6 days, 70 flies at 

 25°, 28.5, and 49 flies at 20°, 40.2. Later in 1917 tbey 

 published another paper in which they give 92.4 days as 

 the average duration of life of 143 flies at 15% and 120.5 

 days of 105 flies at 10° C, together with the t iciiu.iiry 

 distributions from which the averages were »>l)t;iiiiri I. 

 They also present results with different food inixtiircs. 

 and for the two sexes separately, finding that isolated 

 males live a little longer than isolated females, or than 

 the males when mixed with females. 



In another paper in the same issue Northrop (17) 

 gives the results of some expcrini«Miis inulcrtnki'ii to dr- 

 termine the effect on the duration of life ol' the iiiiauo 

 of prolonging the life of the larva by iiiadi'qnaU' feeding 

 (omitting yeast for different lengths of time). In this 

 way the embryonic periods were prolonged from 8 to 17 

 days, but the duration of life of the adult remained the 

 same in every case, ranging between 10.5 and 11.9 days 

 at 27.5° C, at wliich t(-m|u-ratniv tlio four oxpcriiiiei.ts. 

 involving 644 flics, were prrfoniird. 



In a recent ])apei- Arendscii lloiii (l^^) gi\i'< a I'l-w 

 observations on duration of life in tlio nical-womi Tcnc- 

 briq molitor. Thirty-two male hvK'\ lo li\ cd an average of 

 60 "days, with a range from 39 to 11::, and :V2 females 

 averaged 111 days, with a range from 89 to 132 days. 



