BEHAVIOR OF FIRE FLIES 267 



diately became more active and apparently considerably excited. 

 Shortly after turning he emitted a flash of light but he did not 

 stop while he glowed as is ordinarily the case when the males 

 are not on the wing. Similar reactions were seen many times 

 in experiments made for other purposes so that there can be 

 no question as to the accuracy of these observations. Moreover 

 this experiment was repeated several times with different indi- 

 viduals and essentially the same responses were obtained in all. 



In a few instances a free male turned toward the glow of a 

 male in the jar, but the response was always much slower and 

 less definite than an orienting response to a female, and invari- 

 ably, if a female glowed after he had started toward the jar 

 containing the males he turned about at once and proceeded 

 toward her, whereas there was never the slightest indication of 

 such a response to a male glow after he had once become 

 directed toward a female. 



These observations, especially the fact that the male, without 

 having glowed at all, sometimes turns at once with scarcely any 

 interval, toward the flash of light produced by the female, 

 seems to indicate quite conclusively that the relation in time 

 between the glow of the two sexes, that is, the fact that the 

 glow of the female usually follows that of the male at a given 

 interval, is not of prime importance in the recognition of the 

 female by the male. 



Thus we have excluded all characteristic differences between 

 the response of the two sexes which might serve the male in 

 distinguishing between them in the mating reactions save possible 

 difference in the duration of the glow. But as was formerly 

 stated no difference in duration could be definitely established. 

 If the male, then, finds the female owing to unequal duration 

 in the glow of the two sexes, as is probable, he must be so ad- 

 justed that he can detect differences too minute to be readily 

 distinguished by the human eye. 



ORIENTATION 



The luminous or photogenic tissue in the female as previouslv 

 stated is confined to a small area on the ventral surface of the 

 third segment from the posterior end. Just before the female 

 glows in response to a flash of light produced by a male she 

 raises and twists the abdomen so as to direct the ventral sur- 



