PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 355 



them. If one antenna be removed the male travels in a circular 

 path instead of going toward the female. If a male without 

 antennae happens to touch a female he immediately shows 

 strong sexual excitement, such as normal males show when 

 brought near females. Scent glands on the abdomen of the 

 female were shown to be the seat of the olfactory attraction, 

 for when the abdomens were removed males were attracted by 

 them and not by the rest of the female. Blackening the eyes 

 produced no change in the behavior. 



Mayer (1900) performed numerous experiments on the moth 

 Callosamia Promethea. He showed that it is odor that attracts 

 the males, and that this odor comes from the abdomen of the 

 female. Interchanging of wings indicated that the marked 

 sexual dimorphism in color, which occurs in this species, has no 

 selective value. 



Kirkland (1896) 5 showed that in the Gypsy moth odor is 

 again the main element concerned, but the wings of the female, 

 as well as her abdomen, have an exciting odor. Mayer and 

 Soule (1906) tried experiments on this form, which they sup- 

 posed indicated that normal females discriminated against males 

 without wings. I find, by applying Yule's (1911) formula for 

 the standard error of the difference, that the difference between 

 the per cent of times winged males paired without resistance 

 and the per cent that wingless males paired without resistance 

 (the measure of sexual selection used by these authors) is 

 almost exactly three times the standard error. This means that 

 the result is not conclusive. Mayer and Soule blinded females 

 and found this apparent discrimation against wingless males to 

 disappear, but the per cent of resistance dropped, as a whole, 

 from 46% in the normal females to 27% in the blinded ones. 

 This may mean that the blinded ones were too greatly disturbed 

 by the blinding to pay much attention to what male mated 

 with them. While I am inclined to suspect that there is some 

 odor connected with the male's wings, still, as stated above, it is 

 not certain that any effect at all is produced by removing the 

 wings of the male. Further evidence against the importance 

 of sight is furnished by the fact that females did not discrimi- 

 nate against males with wings painted in unusual colors. 



5 I have not seen this paper, but make the statement on the authority of Mayer 

 and Soule (1906). 



