644 NEW SPECIES OF LAMPYRIDiE, 



established that the light is produced by the slow oxidation or 

 combustion of a substance supposed to be phosphoretted hydrogen, 

 which is formed under the influence of the nervous system, and 

 that the seat of light is the parenchymatous cells of the super- 

 ficial layer of the light-organs, and not in the terminations of the 

 tracheae which thickly traverse them. These conclusions are 

 borne out by the experiments of Emery, "^ who states that when 

 the luminosity is only at half its full power the combustion is 

 exclusively confined to these cells. It is only necessary to allude 

 to the power possessed by these insects of extinguishing their 

 light at will,! a power which they can only exercise for a short 

 period, probably just so long as the air can be shut away from the 

 abdominal light-organs ; but I should like to add a few remarks 

 concerning the external appearance of the light of the species 

 here called Aty2:)hella lychnus, which I had an opportunity of 

 observing in the garden of Mr. E. C. Merewether when visiting 

 Mt. Wilson in January last. At that time the insects were to be 

 found in fair numbers on dark still evenings, and a beautiful 

 sight they made, moving in lazy flight between the tree-ferns, 

 their light alternately glowing and disappearing as they 

 approached. This alternate emission and cessation of the 

 phosphorescence appears to be characteristic of many species of 

 Eastern fire-flies, and is supposed by von Siebold to coincide with 

 the movements of inspiration and expiration. I observed that 

 the gleams of light, both in flight and when the insect was at 

 rest, lasted from about one-third to about two-thirds of a second, 

 and that the intervals of darkness were of slightly longer dura- 

 tion ; the light began as a feeble yellow glow, and gradually 

 increased in intensity until it burst into a brilliant reddish- 

 yellow flame. As I have said, the fire-flies were common during 



* Bull. Soc. Ent. Ital., xviii., p. 351 (1885) ; also J. R. Micr. Soc. (2) vi. 

 p. 234 (1886). 



+ The idea that the " source of light " is withdrawn from the external 

 wall of the luminous parts during the interval of darkness, and pressed 

 against it during the period of light, put forward by Gorham (Tr. Ent. 

 8oc. Lond., 1880, p. 66), is, of course, a mere assumption, and is opposed to 

 the structure of the light-organs. 



