674 Comparative Animal Physiology 



Other well established cases of the use of light production as mating sig- 

 nals ha\e been described for \arious species of fireflies.'' In many species 

 the females, which may e\en be wingless, remain in the grass v\ hile the males 

 fly about. The females signal in respjnse to the flashing males, which then 

 fly toward the females. The various species differ in characteristics of their 

 Hashing, such as in the frec|uency, total number of flashes, color, intensity 

 and duration of each flash, etc. 1 he female resjx)nds in a characteristic 

 manner to a flashing of the male of the same species. The female of Pho- 

 timis, for example, always flashes about two seconds after the flash of the 

 male. The male continues to respond to the females until the two sexes ha\'e 

 met. The attracting light response of the female can be imitated b\ use of a 

 flashlight which is operated to flash with the temporal characteristics of a 

 typical responding female for a species. 



Numerous other suggestixe examples of a role of luminescence in the 

 mating reactions of animals have been described, but most of them require 

 more convincing descriptions, or experimental stud\, before they can be 

 definitely accepted as such. However, inasmuch as it is difficult to imagine 

 anv functional significance of bioluminescence in bacteria or fungi, we 

 probably can assume that bioluminescence in man\ animals, especially lower 

 ones, is fortuitous and of no survival value. In these instances light may 

 have appeared as a by-product associated with oxidative metabolism. 



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