40 



males, are extraordinarily large and well developed (?.//., La}ii]>i/ris, 

 Photinuif, Lueiola, etc.), but the antennre are simple. In the non- 

 luminous species, on the other hand, the eyes are of more normal 

 size, but the antenna? of the male are frequently strongly plumose 

 (ej/., Cladodes, Laiiiprocero, etc.), a feature that in this order as in 

 the Lepidoptera is usually regarded as indicative of a highly 

 developed sense of sex-perception in this sex, correlated with the 

 possession of sluggish and retiring habits on the part of the female. 

 It is noteworthy that in the genus P/u'vi/odes, both the plumose 

 antenna? of the male and the powers of luminosity of the female are 

 unusually well developed. 



Undoubtedly the chief function of the light is in securing the 

 mating of the sexes, biit that this is a secondary function only is 

 evidenced by the different degree to which the use of the light is 

 developed. Its wide occurrence within the family proves that the 

 power of emitting light must have arisen early in the evolution of 

 the family, though exactly how it originated is impossible to say. 

 Possibly, it may have served at first as an indication of unpalata- 

 bility, common to both sexes''', and then, coming under the influence 

 of sexual selection as an evolutionary force, have developed along 

 the various lines we see indicated. In connection with their 

 unpalatable qualities, it may be noted that the Lampyridte is a 

 family that has many mimics in other families of beetles, amongst 

 the Telephoridre for example, and the longicorns. Species of the 

 longicorn genera Aiiip/iidiii/cha and l>a(h)}/rliiis, even go so far as to 

 have a ventral pseudo-luminous patch resembling the luminous 

 patch of the fire-flies, but in the allied genus Alinnpyn's, where the 

 dorsal mimicry is quite as close, this patch is lacking. 



The light may also have a certain bionomic value on the principle 

 of " warning coloration," or it may even serve to scare away 

 enemies. A case is on record"'' of a firefly in India alightins near a 

 couple of rats which at once scampered off'. It has been noted, too, 

 that the Indian bottle-bird will plaster some. of these insects about 

 the entrance to its nest, but this is, perhaps, by way of ornament, 

 rather than to scare away would-be depredators. 



On the other hand, in Jamaica, the bnll-frogs are known to eat 

 them, and Henslow speaks of a cat that would search for and eat 

 glow-worms. 



Apart from its principal function in securing the proper mating 

 of the sexes, the light seems also to be largely used, at any rate by 

 the males, for purposes of display. Where the powers of luminosity 

 are largely developed in this sex the emission of the light is usually 

 of an intermittent flashing type. It has been noticed in various 

 parts of the world that these flashing males tend to congregate in 

 large companies, and that all the individuals of one of these 

 gatherings will flash in concert. All the fire-flies around one tree or 

 group of trees, for instance, will flash together, while those around a 



* Henslow in " Nature," 1879, p. 220. 



