306 The Ecologic Relations of the Photogenic Function among Insects. 
Some interesting speculations as to the phylogenetic relations of 
the Lampyridae and other luminous insects presents themselves here, but 
we have so little evidence in any direction that even speculation seems 
hardly justified. Olivier (15) has called attention to the main features 
in the geographic destribution of the Lampyridae. The relatively immense 
number of species in South America — nearly half of the 1200 described 
species — is especially interesting and probably significant. The relati- 
vely scareity in Africa is also noteworthy. On the wohle the Lampyridae 
show the same pecularities in dispersal as are found among other crea- 
tures; — e. g., the genus Pstlocladus, whose species are found only in 
South America and in Japan. 
A second interesting group of luminous Coleoptera are the mem- 
bers of the Elaterid genera Pyrophorus and Photophorus. These two 
. genera are very close, and while little is known as to the habits of 
Photophorus, it is not improbable that it will prove very. much like 
Pyrophorus. Lund (8) and others have shown that Pyrophorus is strongly 
attracted to a moving light, and we are probably safe in assuming that 
in them the luminous power plays the part of an attraction between 
the sexes. Photophorus presents one of those remarkable peculiarities of 
geographie distribution, oceurring as it does in the Fiji and nearby is- 
lands, some eight thousand kilometers from its nearest luminous rela- 
tives in South America. 
Phengodes has already been referred to under the Lampyridae; 
the peculiar structures of these insects, the vast differences between the 
sexes in the adult stage, etc., has long made them a matter of consi- 
derable entomologic interest; with them stands, in this regard, Dioptoma 
adamsıi, before referred to. The New Zealand Bolitophila luminosa seems 
to be about the best known of the non-coleopterous luminous insects, 
and presents the only definitely known instance of proven self-lumino- 
sity in the entire order of Diptera. 
It it probable that among all the brightly luminous members of 
the family Lampyridae, the luminosity serves as a means whereby the 
sexes may meet; it also seems very probable that this is the utility of 
the photogenie function in all luminous Coleoptera, and indeed in all 
self-Juminous insects. Among others luminous forms, — Annelids, fish, 
crustaceans, etc., — this may sometimes be the ecologie relation of the 
function, though in particular instances the defensive and other relations 
may also enter in. 
l. Barber; Phengodes in the vicinity of Washington, D. C.; Proc. Ent. Soc. Wash., 
1906, Vol. 7, pp. 196—197. 
. Emery; La luce negli amori delle lucciole; Bull. Soc. Entomol. Ital., 1886, 
Vol. 18, p. 406; Stett. Entomol. Zt., 1887, Vol. 48, pp. 201—206. 
. Galloway; A case of phosphorescence as a mating adaption; School Sci. 
and Math, Decatur, IIl.. May, 1908. 
. Galloway and Welch; Studies on a phosphorescent Annelid, Odontosyllis 
enopla Verrill. Trans. Amer. Micros. Soc, 1911. Vol. 30, pp. 18—39. 
5. Gorham; The structure of the Lampyridae with reference to their phospho- 
rescence; Trans. Ent. Soc. Lond., 1880, pp. 63--67. : 
6. Green; Luminous Coleoptera from Ceylon; Trans. Ent. Soc. Lond,, 1912, 
. 717—719. 
7. TubnSoh Origin and metamorphoses of Insects; Lond., 1874, p. 17. 
8. Lund; On light reactions in certain luminous organisms; Johns Hopkins 
University Circular, 1911, No. 2, pp. 10—13. 
Ed ed 
