BEHAVIOR OF FIRE FLIES 269 



The accuracy of orientation in these reactions is really sur- 

 prising. In making observations with reference to this point 

 the female was usually put into a glass vial 2 cm. in diameter. 

 This was set over a circle of equal size on a sheet of paper spread 

 out on the ground. Males flying about were ordinarily soon 

 attracted by the female and lit on the paper, sometimes very 

 near the vial or on it, at other times 30 to 40 cm. away. In 

 orienting after they lit they seldom failed to become directed 

 toward a point within the circle under the vial no matter whether 

 the female was removed immedi itely after she glowed or whether 

 she was not removed at all. 



The male usually does not begin to turn toward the female 

 in response to her glow until the illumination has entirely dis- 

 appeared. Thus, in the total absence of the flash of light which 

 caused the reaction he turns through the proper angle, that 

 is, he orients and proceeds toward the spot where the flash oc- 

 curred. How is this possible? Does it mean that the male 

 fire-fly can locate objects in space, that he has a spacial sense, 

 that he knows and remembers the extent of turning necessary 

 in order to direct his longitudinal axis toward any given point 

 in space? 



If we assume, just as in the case of the female, that there is 

 in the male a specific response for the illumination of every 

 surface of the eye; that is, that momentary illumination of the 

 posterior surface is followed by turning through 180 degrees 

 and then locomotion straight forward, the side of the eye by 

 turning through 90 degrees and then forward movement, the 

 front of the eye by forward movement alone, etc. It is not 

 difficult to conceive all of these reactions to be purely mechan- 

 ical, reactions of the nature of unconscious reflexes. 



Whether or not the production of light in these insects is a 

 sort of by product of metabolic changes, as maintained by 

 many, it is evident that it is of fundamental biological sig- 

 nificance. Indeed it is safe to say that its elimination would 

 result in the destruction of the race and yet the light in itself 

 can be of no special importance. The essence in the response 

 of the male, like that in the response of the female, is not light 

 but what light represents, that is, an individual of the oppo- 

 site sex. 



Males were at different times exposed in continuous illumi- 



