484 



THE AMERICAN NATURALIST [Vol. LV 



longevity is not known, so that the results have little sig- 

 nificance from the standpoint of exact studies. The 359 

 insects had at 72° F. an average longevity of 4.8 days with 

 a maximum of 15 days, at 62° F. an average of 6 days 

 with a maximum of 28, and at 42° F. an average of 10.9 

 (lays with a maximum of 39. For the second part of the 

 experiment 184 larvae of the oak-tree moth were used. 

 The results are too conflicting to allow one to draw any 

 definite conclusions. 



TABLE I 



I 272 j 42 I 128 | 89 j 



).5 26.9 47.8 



In 1915 appeared Lutz's (13) paper on natural selec- 

 tion in which he finds in each sex a slight negative correla- 

 tion between the length of adult life and the duration of 

 the embryonic periods. The distributions which he has 

 for normal length of adult life with varying temperature 

 give the 250 J's an average duration of life of 36.3 days, 

 and the 263 $s an average of 28.9 days. He also gives 

 distributions in hours of duration of life of flies which 

 were given water but no food, and the correlations of 

 duration of life of these starved flies with wing measure- 

 ments. 



During 1916 and 1917 Loeb and Northrop (14-16) pub- 

 lished a series of papers on the effects of food and tem- 

 ] .crature on duration of life in Drosophila. The first pre- 

 liminary paper in 1916 gives the duration of life of cultures 

 of Drosophila in water and in cane sugar at temperatures 

 from 28^ to 9° C, showing a temperature coefficient for 

 the duration of life of about the order of magnitude of 

 that of chemical reactions, namely of about 2 for a dif- 



