The Ecologic Relations of the Photogenic Function among Insects. 303 
The Ecologiec Relations of the Photogenic Function among 
Insects. 
Von F. Alex McDermott, Pittsburg, Pa. 
Among the ngumerous interesting problems connected with the 
emmission of light by living organisnıs are those which center around 
the usefulness of the light-producing power to the organisms themselves. 
For the great majority of luminous creatures no definite conclusions 
as to the utility of the luminosity can be reached, although there are 
good reasons for considering that it is probably defensive, alluring etec., 
in function, in various groups. 
In at least two phyla, howewer, it has been possible to arive at 
a definite explanation of the usefulness of the photogenic function during 
the life of the organisıns: 
Among the Annelids, Galloway ı3) and Galloway and Welch 
(4) have shown that the luminosity serves as a mating adaptation in 
Odontosyllis enopla. Recently Potts (17) has called attention to the 
similar habits of Odontosyllis phosphorea, in which the luminosity 
appears to play a more subordinate part in mating. Lund (8) has also 
made observations on marine annelids. 
It is among the insects, however, that we have the most definite 
cases of the application of the light-producing power to lives of the 
'organisms. Among the Coleoptera there is the family Lampyridae, in 
which a very large number of the species possess the photogenic function, 
The surmises as to the usefulness of this function to these insects have 
eınbraced the protective, alluring and reproductive ideas, but itis now 
known that in at least certain of the genera of Lampyrids, the photo- 
genic function serves, as in the ÖOdontosyllids mentioned above, as & 
mating adaptation. Among the older writers, Spallanzani (18) and 
Rennie (19) both called attention to the attraction between the sexes 
apparently as the result of the luminosity, though the latter writer is 
inclined to interpret his observations as rather opposing the theory of 
the significance of the function for mating. Lubbock (7) notes a si- 
milar instance, 
The first conclusive observations were made by Osten-Sacken (16), 
on the American species Photinus pyralis. ÖOsten-Sacken found that 
the females of this species remained clinging to grass, leaves, etc., while 
the males flew above them, flashing at intervals.. When the flash of a 
male was seen by a female, she answered by flashing, and upon the 
male seeing this answering flash, he alighted near the female, finally 
locating her definitely through subsequent flashes, and mating with her. 
Next chronologically were the observations of Emery (2) upon 
Luciola ilalia. Emery watched the actions of the sexes in this species, 
and concluded that they depended upon the use of the luminous power 
for meeting and mating. He then tried a number of experiments, and 
found that females enclosed in a perforated opake box did not attract 
males, while those enclosed in glass vials did, thus excluding the effect 
of odors. 
Östen-Sacken’s paper was not well known until recently, and 
his observations were accordingly fequently overlooked, he records, ho- 
wever, what is probably the first definite establishment of the ecologie 
relations of the photogenie function in any species. Not knowing of 
