322 
COLEOPTEUA. 
throve in captivity. The luminosity is not used in feeding; the insect 
seizes a snail, curls over on its back with the snail held in its legs and 
slowly devours the muscular part, leaving the alimentary canal. 
This has been observed frequently and the luminous organ is not func¬ 
tional. What purpose this organ serves in a larval insect is not clear 
unless it be defensive. Quite young specimens exhibit it and though 
none of these larvae have been reared, all that have been observed in 
India are sexually immature and evidently larval. It is to be hoped 
that these curious insects will be investigated by an observer situated 
where they are abundant and that the species to which they belong 
may be determined by rearing them to maturity. Olivier states that 
while the larvae are well known, in no single case has a larva been 
reared and the imago identified. A larva, apparently of this group, 
was found in Behar (Figs. 199, 200), an elongate, slightly flattened 
insect, of a dull reddish tint with soft integument ; the legs were well 
developed, and at the apex of the abdomen below were two light-emit¬ 
ting patches. Apparently this was a mature larva seeking a place in 
which to hibernate or pupate. 
The nature of the luminosity of these insects has been much dis¬ 
cussed ; certain tissues of the bodies of these beetles have the power 
of giving off light, just as other tissues exert a mechanical action or 
emit electrical energy. The luminosity is under the control of the 
insect and heat is not produced. It has been remarked that these in¬ 
sects can convert a quantity of energy into its full equivalent of light 
without loss due to the production of heat; no means are known of 
doing this artificially and even the most modern devices for light pro¬ 
duction convert only a fraction of the energy into light. The precise 
object of this luminosity is not clear ; while most of the beetles are noc¬ 
turnal, a few are actually diurnal in habit and the luminosity would not 
appear to have any value. In the case of nocturnal species, the emis¬ 
sion of light may serve as a “ warning signal ” to bats and nocturnal 
birds but there is little to support this view. It is more likely that 
this property is connected with sex, but it is also possible that it is a 
part of the vital activity of the insect which has no function but an 
ornamental and pleasing one. It is worth noting that the luminosity 
is greatest in those species which have the least developed antennae ; 
forms with long pectinate antennae are the least luminous. 
