;*12 THK rAN.M>I AN KNTOMOI.CMMHT. 



What the suhsianceis that is buriu-d to produce tliis light we do not 

 know. A large numl)cr of cheniicils and mixtures of chemicals have been 

 foimd to give light under certain conditions, usually of oxidation. One of 

 these (formaldehyde and pyrogallol, oxidized by strong hydrogen peroxid 

 solution), investigated by Max Trautz (Zeitschrifl f. physikal. Chemie, 

 1905, Vol. 53, pp. i-iii). produced a light whose spectrum appears to 

 roughly approximate that of the firefly. 



In this connection I have found that the spectrum of the light pro- 

 duced on moistening with commercial three-percent, hydrogen peroxid 

 solution, the ground luminous tisnie oi \.\\q pyra/is, which has been dried 

 in hydrogen over sulphuric acid, extends only from 9 to 15 of the scale of 

 the spectroscope ; that is, it lies mainly in the yellow and yellow orange 

 portions of the spectrum. 



Some as yet imfinished histologic studies indicate ihat the structure 

 of the photogenic organs of Photinus pyralis and Phoiurii peniisylvanica 

 are approximately the same, and mujch as described by Townsend 

 (American Naturalist, 1 904, Vol. 38, pp. 1 2 7- 1 5 1 ), for Photinus marginellui- 



The question naturally arises, "What is the purpose of the light- 

 emission ?" That this phenomenon has some relation to ihe sexual 

 function is scarcely to be doubted. Just why this family should possess 

 this power, while it is limited to occasional members of other families and 

 of other orders of insects, that is, just what conditions of life and environ- 

 ment render it necessary as an adjunct to the sexual function, is not yet 

 determined. Ehrenberg, in his extensive work, 'Das Leuchten des 

 Meeres" (.\bhandl. d. k. Akad. d. Wissenschaften, Herlin, 1 834-1836, pp. 

 411-575), agrees that, while the exphnation that the luminosity is an 

 adjunct of the sexual function is acceptable for the Limpyridn? and other 

 bisexual forms, it will not hold for the hermaphroditic marine organisms 

 that are luminous, while Watase' (Protoplasmic contractility and Phosphor- 

 escence, Hiol. Lectures, Wood's Hole, 1898, pp. 177-192) seems to leave 

 one with the impression that he regards phosphorescence as a potential 

 properly of all protoplasm. I have no further explanation to offer in this 

 connection, but the following chance observation may be ()f interest : 



I was looking over a fence down a sloping field, a little later in the 

 evening than the period of greatest activity on the part of the pyralis. 

 There was no sign of luminosity nearby, though some dist.ince awiy 

 several males of the pyralis were flying about. One of these flew towards 

 the fence, and then dropped- downward, giving his characteristic dipping 

 flash. Immediately the less intense lights of several pyralis females 

 appeared in the nearby weeds, where their presence hid theretofore not 



