BEHAVIOR OF FIRE-FLIES (PHOTINUS PYRALIS)? 



WITH SPECIAL REFERENCE TO THE 



PROBLEM OF ORIENTATION 



S. O. MAST 

 The Johns Hopkins University 



INTRODUCTION 



The production of light in living tissue, although confined 

 to relatively few species, is widely distributed among living 

 •organisms. It is rather common in molds and bacteria and 

 it is found in representatives of all classes of animals including 

 vertebrates where it is especially common among certain groups 

 of fishes. 



In some cases, the molds for example, it is exceedingly dim- 

 cult to conceive of any possible biological significance that lumi- 

 nescence may have. In others it is highly probable that it is 

 • closely associated with fundamental phenomena in the life of 

 the organisms. All sorts of suggestions have been offered with 

 reference to the function of the production of light in different 

 species. In some it is considered to be mainly a secondary 

 sexual characteristic; in others it is supposed to serve primarily 

 as a lure for prey ; and in still others as protection against enemies. 

 Among the. most novel of such suggestions that I have seen is 

 •one presented by Dubois, a prominent naturalist, who main- 

 tains that certain tropical birds capture fire-flies and fasten 

 them to the soft clay walls of their nests and that the light 

 which they produce while thus situated protects the nest against 

 snakes. 



While some of the hypotheses which have been offered will 

 probably eventually be found to hold for many different species, 

 only in very few cases has the function of luminescence thus 

 far been well founded, in fact, it has been clearly established 

 •only in one case. 1 Galloway found (1908) that in the annelid, 



1 After the main part of this paper was completed there appeared an article 

 by McDermott, in the Canadian Entomologist, Dec, 1911, in which the author 

 presents strong evidence in support of his contention that luminescence in the 

 fire-flies, Photinus pyralis, P. scintillans, and P. consanguineus, functions primarily 

 .as a secondary sexual character. In this interesting paper McDermott also calls 

 attention to observations made by Osten-Sacken on Photinus pyralis in Washing- 

 ton, D. C, 1861. These observations, which were described in the Stettiner Ento- 

 mologische Zeitung, also demonstrate fairly conclusively that in this species the 

 production of light functions in mating and this appears to be the first record bear- 

 ng on the biological function of this phenomenon that is in any way conclusive. 



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