SOME SOCIAL WASPS 271 



by 9 : 15 the next morning ; the other did not appear until 

 2 : 30. The wasps from nests 21 and 28 may have returned 

 the same day, but the follow-up did not occur until the next 

 morning at 9: 15. 



From nest 19 one worker and two males, used for the first 

 time, were taken and marked in yellow. At 4 p. m. the 

 same day the worker arrived home; the males did not 

 return. 



Nest 13, one male which did not return. 



Nest 26, three workers, none of which returned. 



Nest 10, ten males and five workers. None came back. 



Late in the season, when the cells are empty and workers, 

 males and queens abound, one would not expect the wasps 

 to maintain any interest in the nest or to exert themselves 

 to return to it, but the problem is worthy of careful in- 

 vestigation. In this experiment, none of the males re- 

 turned. If the young workers easily get lost, how much 

 more likely are the males to do the same. 



If some unknown factor automatically draws the work- 

 ers back to the hive in the sense of Bethe's theory, it should 

 likewise possess the same chemical or physical affinity for 

 the males. 



Experiment XV 



September 4. This experiment is the same as Experi- 

 ment XIV, except that the material was such as could be 

 gotten at the end of the season, and the wasps were held 

 captive over night. They were gathered at 5 p. m. on Sep- 

 tember 3, fed on honey, of which they ate ravenously, and 

 liberated at the mail-box at 8 .'30 a. m. It rained during 

 the intervening night and the morning was cloudy, but the 

 afternoon was bright and sunny. 



Nest 25 contributed five workers and two males, all new 

 to the experiment, one queen with a white dot used 



