BEHAVIOR OF FIRE FLIES 261 



and proceeds. If the female does not respond, as frequently 

 happens, he retains the attitude of attention for approximately 

 a second and then continues on his course without turning. 



The female glows in response to artificial light as well as to 

 the glow of the male. In fact the response is apparently inde- 

 pendent of the character of the light. I was able to induce it 

 by flashes of light produced by means of an electric pocket 

 lamp, parlor matches, tallow candles, kerosene lamps, sun light, 

 light reflected from objects of various kinds, light passed through 

 a plate of ruby glass or through a solution of copper sulfate. 

 It is, however, dependent upon the duration of the illumination. 

 The female will respond by glowing only if the light is turned 

 on, left a certain length of time (a fraction of a second) and 

 then turned off. She will not glow if it is not turned off after 

 the proper exposure. This response is then clearly not due to 

 light in itself but to changes in the intensity of the light. But 

 it is equally clear that the essential factor in the response of 

 the female is not changes of intensity but what such changes 

 of intensity ordinarily represent, that is, the male. 



A number of the characteristics in the behavior of the fire- 

 flies described above, as well as others are clearly brought out 

 in the following quotation from my note book: On July 8 a 

 female was caught at 8:15 P. M. and placed on the end of a 

 pencil. Here she remained for fifteen minutes, almost perfectly 

 quiet, while I moved the pencil about freely in studying the 

 orienting reactions of several males on a sheet of paper. She 

 was then taken to the porch, where I sat a short distance from 

 the railing holding the pencil in my hand. I watched her care- 

 fully until 9:15, that is, for forty-five minutes. During this 

 whole time she retained the same position and glowed only in 

 response to flashes of light produced by males which occasion- 

 ally chanced to fly near. The farthest distance of a male to 

 which she responded was six meters. After I had been on 

 the porch twenty minutes a male, attracted by the glow of the 

 female, flew in and lit on the railing. Here he crawled about 

 for nearly twenty-five minutes, glowing periodically at irregular 

 intervals. One series of successive intervals recorded in seconds 

 reads as follows: 35, 8, 12, 16, 5. The male turned toward the 

 female every time she glowed in response to his illuminations, 

 which was about two out of three times, but he could not get 



