THE LIGHT OF FIREFLIES. 



'The rays emitted by the common fireflies are re- 

 markable in being almost entirely light rays, with almost 

 no thermal or actinic rays. According to Young and 

 Langley, the radiations of an ordinary gas-flame contain 

 less than three per cent, of visible rays, the remainder being 

 heat or chemical rays, of no value for illuminating purposes; 

 while the light-giving efficiency of the electric arc is only 

 ten per cent, and that of sunlight only thirty-five per 

 cent. The light of the firefly, however, may be rated 

 at one hundred per cent.; this light, then, is perfect, and 

 as yet unapproached by artificial means. 



"As to the use of this luminosity, there is a general 

 opinion that the light exists for the purpose of -sexual 

 attraction a belief held by the author in regard to Pho- 

 tinus, at least. Another view is that the light is a warning 

 signal to nocturnal birds, bats, or other insectivorous 

 animals; this is supported by the fact that lampyrids are 

 refused by birds in general, after experience; young birds 

 readily snap at a firefly for the first time, but at once 

 reject it and thereafter pay no attention to these insects." 

 In some species the eggs, also, are luminous. 



The Lampyridas may be divided into four subfamilies: 

 Lycinas, Lampyrinae, Telephorinas, and Drilinae. 



The Lycinas have the middle coxas rather widely sepa- 

 rated by the mesonotum. The elytra usually have a 

 coarse network of fine elevated lines. The head is some- 

 times prolonged in front of the eyes into a long, narrow 

 beak. The antennas are usually conspicuously saw-toothed 

 or comb-like. 



Lycostomus lateralis: about .4 in. long; black, with the 

 sides of the pronotum, the shoulders, and the front half of 

 the margin of the elytra, yellow. 



Calopteron: the elytra gradually widen from base to 

 apex and each has six longitudinal ridges (costas) ; antennae 

 saw -toothed. C. terminate is .5 to .7 in. long; black, 

 except for the yellow basal half or two-thirds of the elytra 

 and a very narrow margin of yellow on the sides of the 

 pronotum. C. reticulatum and typicum are about the 

 same size as termi-iale, but the pronotum, especially of 

 reticulatum (Plate LXXVIII), is broadly margined with 



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