262 S. 0. -MAST 



to her without cither flying or crawling down to the floor and 

 then up on my leg. He did neither and consequently did not find 

 her, . although he was still active when the observations closed 

 at 9 :i 5 . At that time the pencil containing the female was 

 stuck into a crack in the wall at the back of the porch, about 

 six feet from the floor, and left. At 2:20 A. M., the following 

 morning, a male was found copulating with her. At 5:15 the 

 male had left but the female was still on the pencil and had not 

 moved. At 6 she was still there but at 7 she had disappeared. 



FUNCTION OF LUMINESCENCE 



Our description of the behavior of fire-flies demonstrates 

 conclusively that luminescence functions in bringing opposite 

 sexes together for the purpose of copulation. The following 

 experiments show that this is the only factor involved in the 

 phenomenon, that vision and smell play no part in it. 



If a female is placed on the end of a pencil or small -twig she 

 remains quiet, as stated above, sometimes for many minutes 

 and thus she can be readily transferred to any point desired. 

 In studying the orienting reactions of the males on a sheet of 

 paper I frequently made use of this method in handling the 

 female. Under such conditions both respond normally and if 

 not disturbed they soon come together and copulate. 



In these experiments I repeatedly held the female near the 

 male and found that if she did not glow there was no indication 

 of any response unless his antennae actually came in contact 

 with her. Thus I have often seen a male, in running about, 

 come within a centimeter of a female without the slightest 

 appreciable change in his course and then after continuing 

 several centimeters, sometimes twenty or more, turn about in 

 response to her glow and proceed directly toward her. Some- 

 times, however, the males were seen to turn toward the female 

 when they came near her; but I found that they turned toward 

 the pencil quite as often when it did not contain a female. Con- 

 sequently, while the turning of the male in these cases is evi- 

 dently due to the presence of an object it is clear that he does 

 not recognize the female by vision and that images of objects, 

 if such are actually formed, play a very insignificant part in 

 the process of mating. 



In some insects mating appears to be controlled very largely 



