BEHAVIOR OF FIRE FLIES 263 



by chemical diffusion from the female. Mayer (1900) found 

 this to be true for certain butterflies. The observations de- 

 scribed above show that if diffusion of chemicals functions in 

 the mating of the fire-flies studied, the chemicals must be emitted 

 only in connection with the production of light. But that 

 chemicals which may be thus emitted are insignificant in the 

 process of mating is shown by the fact that if the females are 

 enclosed in air-tight glass jars as was repeatedly done, the 

 male finds them quite as readily as when they are free. (See 

 experiment described below.) It is consequently clear that 

 aside from actual contact the flashes of light produced by the 

 fire-flies are alone functional in directing the male to the female 

 in mating. 



However, as previously pointed out for the female, so also 

 for the male the responses preliminary to copulation are not 

 primarily due to the effect of light in itself or to the effect of 

 changes in the intensity of light. The responses are clearly 

 given with reference to something which the flashes of light 

 represent, a sexual phenomenon, preservation of the race, etc. 

 Thus the fire-fly, although probably not conscious, acts with 

 reference to the future. It may be said to project its present 

 into the future, to live in the future as well as in the past and 

 the present. 



RECOGNITION OF THE FEMALE GLOW BY THE MALE 



In many species the illumination produced by the male 

 differs markedly from that produced by the female. In some 

 the glow of the male is much more intense than that of the 

 female. In others there is a marked difference in the duration 

 of the glow of the two sexes. In still others the illumination 

 has certain peculiar distinguishing characteristics, as, e.g., in 

 Photinus sanguineus in which the male glow consists of two 

 flashes of light separated by a short interval, while in the female 

 it consists of but a single flash. In the Western Maryland spe- 

 cies 4 I was unable to distinguish between the glow of the two 

 sexes either in the quality or in the intensity of the light or in 

 the duration or the nature of the glow. At times it did, indeed, 



4 McDermott (1911, p. 400) referring to Photinus pyralis says: "The flash of 

 the female, while of the same colour as that of the male, is easily recognized after 

 a little practice, being slower — or rather of longer duration — and less intense." 



