113 



Inheritance of the Length of Life in Drosophila 



ampelophila. 



RoscoE R. Hyde. 



1. INTRODITCTION. 



I litive ]>een experimeuting with two different strains of the fruit fly 

 that differ to a marked degree \A'ith respect to the length of life. The 

 first or Inbred stock lives an average of about 37 days. The second or 

 Truncate stock lives an average of about 21 days. In both stocks the aver- 

 age life of tbe male is somewhat longer than that of the female. It is the 

 puiijose of this paper to show the behavior of the shortened length of life 

 of the Truncates in heredity. The evidence bears especially on the be- 

 havior of the Fi and I'\, generations that result from crossing the Inbred 

 and Truncate stocks. I shall also present evidence that bears on the ques- 

 tion as to whether or not any relation exists between the length of life and 

 the number of offspring produced by these flies. 



The data upon which this paper is based grew out ot a study of fertil- 

 ity and sterility in these strains. It was found necessary in connection with 

 these studies to keep a careful record of the length of life of the parents. 

 This paper is an analysis of that record. The data includes the record 

 of 898 individuals that were bred in pairs from September, 1911, to April 

 1913. 



The flies were in all cases used as the parents of the next generation 

 and consequently bred in pairs. Accordingly a male and a female were in 

 each case exposed to exactly the same envu'onmental conditions. It is not 

 to be overlooked that the flies live for several weeks, and since the pairs 

 were constantly being made up the environmental influences would be 

 practically constant. I made it a rule to transfer these flies to new bottles 

 every ten days. It is necessary to transfer the parents more frequently 

 in very warm weather, since offspring will hatch which canijot be distin- 

 guished from the parents.* As a matter of fact it is safe to say that in 



* I have had Drosophila ampelophila to complete development from the egg to a fully formed fly 

 within seven days at Woods Hole, Mass.. in July, 191.3. 



8—1019 



