298 



POPULATIONS 



fruit fly, Drosophila melanogaster, and the 

 flour beetle, Triholium confusum, have 

 been studied perhaps with greatest preci- 

 sion. Since tables for Triholium furnish a 

 creditable illustration for our present pur- 



the male." Under the conditions reported, 

 the males had a mean life duration of 177.8 

 days (a median of 171.6), while the fe- 

 males lived 198.5 days (a median of 

 210.7). These differences are statistically 



FEMALES 



20 



30 40 50 



AGE IN YEARS 



90 



Fig. 91. Death rate curves (lOOOgj^) for white males and females in continental United States, 



1929 to 1931. 



poses and provide certain background data 

 about this important "population organism" 

 later to be discussed in various connections, 

 the data on this form presented by Pearl, 

 Thomas Park, and Miner (1941) will be 

 briefly reported here. 



As for most species, the Triholium female 

 is longer-Uved in the statistical sense than 



significant. The Triholium example is best 

 presented by means of h, dj^ and lOOOq^ 



* Pearl, Park and Miner (1941) review an 

 earlier study of Labitte on mean duration 

 of life in various Coleoptera. Of eighteen 

 different genera, fifteen were instances in which 

 the females outlived the males, and three were 

 instances in which the reverse was true. 



