THE CANADIAN ENTOMOLOGIST. 181 



organic bodies will thus by slow oxidation give such a disproportionate 

 amount of light, we may enter upon a path which leads to the accom- 

 plishment of one of the great desires of civilization, the production of 

 light, without undue expenditure of energy in the development of heat, as 

 a waste product. 



In regard to the manner in which the light is evolved, I have but 

 little information to give, though what I say may serve to correct some 

 erroneous views which have been elsewhere expressed. 



The popular name of these insects, lightening (or lightning) bugs, as 

 distinguished from fireflies* is derived from the fact that the light is 

 intermittent. It is never entirely extinguished, but is paroxysmally weak 

 and brilliant. When seized, under the influence of fear, the intervals 

 become irregular, and the flashes are frequent. When put into alcohol 

 there is at first a fitful and rapid exhibition of light, but afterwards the 

 light becomes moderate and permanent for some minutes. When the 

 light organs are separated and crushed, the light also continues for some 

 time, becoming gradually weaker. 



I therefore infer that the excitement of the light-giving organs to the 

 highest degree of activity is manifested by the supreme effort of the will 

 of the animal, and that the exhibition of light is dependent upon a par- 

 ticular structure, more or less under the control of the will, but containing 

 a special material capable of evolving the light independent of the will. 

 In a similar way to that in which the voluntary muscles of all animals 

 evolve motion, and the special electrical organs of certain fishes evolve 

 electrical currents, so do these organs of the Lampyridae evolve light 

 from some peculiarly constituted structure fitted for the purpose. 



It may be conceded, after what has been said above, that the idea of 

 Mr. Gorham,+ that " the external white vitreous parts are diaphanous, and 

 permit the light to shine through," is perfectly correct, but that his belief 

 that " the source of light within the body of the insect can be pressed 

 against these windows, or retired from them at its pleasure," is quite 

 ' without foundation. 



* Fire flies are Elateridre of the genus Pyroplwrns (Spanish Citcuyo), of which one 

 of the smaller species, P. physoderus, occurs in Florida and Texas, and shine with a 

 constant light, chiefly visible in two vesicles near the hind angles of the prothorax, 

 which are convex, and covered with a transparent chitinous integument. All species of 

 Pyroplwrns are not phosphorescent. 



+ Trans. Ent. Soc. London, 1880, p. 66. 



