356 A. H. STURTEVANT 



Federley (1911) gives evidence indicating that odor is a strong 

 sexual stimulator in the moth Pygaera, and may even cause 

 males to attempt to pair with the bars of the cage in which they 

 are confined. Entomological literature contains many accounts 

 of the remarkable ability of male moths to locate females though 

 smell. A few of the more striking cases are given by Wash- 

 burn ('09, pp. 87 and 88.) 



SEX RECOGNITION IN DROSOPHILA 



It was noted above that when an egg protrudes from the 

 ovipositor of a female any males in the same bottle usually 

 become excited and begin courting. When a female is killed 

 eggs are likely to protrude, and males are often seen vigorously 

 courting females which have been freshly killed, even though the 

 killing agent were so strong smelling a substance as ether. In such 

 cases it is the posterior end of the abdomen which seems to be 

 the chief focus of attraction. The attraction may last for at 

 least 30 minutes after death, and probably longer. I have not 

 as yet been able to cause males to copulate with dead females, 

 probably because the female normally takes an active part, as 

 indicated above. 



If a male which has just paired is placed with a male which 

 has been isolated from females for several days he may be 

 courted by that male, though this is not frequent. If two males 

 are kept in solitary confinement for four or five days and are 

 then put together they often court each other, in one case even 

 the doubling up of the abdomen being seen, and the wing move- 

 ment {not fighting) being almost invariably observed. Such 

 mutual courtship between males has not been seen under other 

 conditions, but a dead male which had not been with females 

 for two days before killing has been seen to be courteql by other 

 males. This courting, however, seems more likely to occur when 

 juices from female abdomens are put on the dead males. In 

 Psychoda sp. courtship of males by males seems to be very 

 frequent, and often copulation is attempted. The genitalia even 

 become attached, and stay so for several seconds. Males have 

 been seen to mount males in Fucellia marina, Sepsis violacea, 

 and Sarcophaga sp. 



In order to test what part is played by the female juices 



