864 MR, NELSON ANNANDALE ON THB [ Dec. 4, 
cannot be in all cases a sexual attraction, for it is exhibited by 
larve and even by eggs'; neither can its object always be to 
attract prey: that it is a warning to enemies seems hardly pro- 
bable, for most small animals, whether aquatic or terrestrial, are 
attracted rather than repelled by light. In the bacteria and 
in forms like Noctiluca it appears to be an adventitious result of 
metabolism rather than to bring any practical gain to the organism ; 
among the adults of the Lampyride it very probably acts as a sexual 
charm ; among the larve of the same group its purpose may possibly 
be to attract prey. In the case of the aquatic form there must be 
some reason why the larvee should come to the surface at night and 
display their light on the top of the water. That purpose can hardly 
be to warn surface enemies not to eat them, or to scare away aerial 
aggressors. Much more probably the light attracts some surface or 
aerial prey. The fact that the light disappears when the water is 
disturbed also supports this view. It is not to the advantage of 
the larve to attract the attention of any animal big enough to make 
a commotion in the pool. 
In three other species of Lampyrid larve, all terrestrial,—two, 
which were both over an inch in length, being found crawling on 
the ground among bushes in Patalung, and the other seated on a 
cocoanut-husk under a house in Kelantan—the light, which was 
situated in all cases on the ventral surface of the abdomen, was 
steady, and neither flickered as it did in the winged forms, nor 
slowly disappeared without apparent cause as in the case of the 
aquatic larva. A small specimen which I found under the mosque 
at Aring, mistaking it at first sight for luminous fungus which grew 
there commonly, continued shining when picked frem the ground, 
but immediately became dark when dropped into formol, and never 
shone again. Professor Poulton tells me that North-American * 
fire-flies lose control of their lights when placed in a cyanide-bottle, 
and are no longer able to extinguish them. The same is true of 
the Malayan winged forms, though occasionally a specimen becomes 
entirely dark for a few minutes when first introduced into the bottle. 
The aquatic larva which allowed its light to reappear after it had 
been in corrosive sublimate for some minutes was probably only 
just beginning to become affected, for corrosive penetrates hard 
chitin very slowly. The insect allowed itself, when once affected, 
to be transferred into a more pungent medium before it finally 
ceased to shine. 
Of all the manifestations of luminescence among animals there is 
none more curious, or, in the present state of our knowledge, more 
inexplicable, than the manner in which large numbers of individuals 
of certain fire-flies are able to display their light with absolute 
apparent simultaneity and unison aad with regular intervals of 
darkness, under circumstances which make it impossible for all the 
members of the swarm to see one another. Even the power, 
1 See Dubois, Bull. Soe. Zool. France, xii. 1887, p. 137. 
2 Darwin makes very much the same remark with regard to the Brazilian 
forms, in his ‘ Voyage of a Naturalist * (p. 30). 
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