PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 357 



mentioned above I placed some on bits of filter paper and put 

 these in the same vial with males. The males paid no atten- 

 tion to the paper, and showed no signs of excitement, though 

 that they were sexually ripe was shown by the fact that they 

 courted and paired with females when they were put in with 

 them. This experiment has been repeated several times with 

 the same result. When a female is thoroughly crushed and the 

 remains heaped up in a little pile the males will sometimes 

 court slightly, but as a general rule, the more mashed the female 

 is, the less excited the males become. No great importance is 

 to be placed upon this latter experiment, as the result is com- 

 plicated by the presence of so many other body juices. This 

 objection, however, will hardly hold in the case of the filter 

 paper impregnated with female juices. The objection that not 

 enough odor was present may perhaps be justifiable in that 

 case. But neither of these objections would seem to apply to 

 the following experiment. Two females were placed in a small, 

 dark, cloth bag and this was put in a vial with a few males. 

 The males were close to the females, which they could not see or 

 touch, but should be able to smell. This experiment was done 

 three times and in no case did the males show any signs of 

 sexual excitement, though in all three cases they did court 

 immediately afterwards when given females in the usual way. 



It has been shown by Barrows ('07) that the sense organs 

 for smell in Drosophila, insofar as one may judge from reactions 

 to food substances, are located in the terminal antennal joints. 

 For this reason I was led to perform the following experiments, 

 in an effort to determine the part played by the sense of smell 

 in courtship and copulation. 



The antennae were removed from several males, 6 which were 

 after several days placed with virgin females. Such males are 

 very sluggish, and- it was therefore not surprising that no court- 

 ship was observed. However, one such male was found copu- 

 lating, and at least three of them left offspring after the opera- 

 tion. One of the three had white eyes, and was therefore prob- 

 ably also blind. Courtship has been observed in two males from 

 which the antennal aristae had been removed. A normal male 

 has been seen copulating with a female from which the antennae 



6 1 have found that antennae may easily be removed without using the complex 

 method described by Barrows, if the operation be performed on very young flies. 



