24 A PHYSICAL STUDY OF THE FIREFLY. 
of consanguineus. It is possible that when subjected toa thorough analysis 
the maximum emission of the scintillans will be found still farther toward the 
red, say 0.58u. From the photometric curve, Fig. 9, obtained by Langley 
and Very,* the maximum emission (not applying the energy curve of the 
comparison source) of the Cuban firefly, Pyrophorus nochilucus, occurs at 
0.5384. ‘Two determinations by Dubois,{ using a grating, gave \=0.53y as 
the point of maximum emission. ; : 
In connection with the much-discussed question of the physiological effect 
on the eye, it is of interest to note the description, by Dubois, of the varia- 
tion in the color of the light emitted by Pyrophorus. He says that when the 
light diminishes in intensity the red and orange rays disappear and at last 
T T T are | T 
Plate 5,26,’ll 4 
5,27,7ll_ 
6,19, 1! OO 4 
6,20,’11 6 
Emissivity 
oO 
} i 
! \ 
52 4 6 8 60 EyT} 
Fic. 10.—Spectral energy curves of fireflies and glow-lamp. 
only the green rays persist; and that when the animal begins to emit light 
the green rays first appear, then the color extends farther and farther into 
the red, when the light attains its maximum intensity. 
In concluding this section it may be added that for the first time we have 
substantial evidence that the color of the light of various fireflies is different, 
the maximum emission varying from o. 55u in the bluish light of the Photuris 
pennsylvanica to 0.584 in the orange-red light of the Photinus consan guineus. 
Evidently, in these extreme cases the eye made no serious mistake in assign- 
*Langley and Very, Amer. Jour. Sci. (3), 40, 1890. Smithsonian Mis. Collections 
No. 1258, 1901, 
tDubois, Legons de Physiologie générale et comparée, Paris, 1898. 
