FIREFLIES AAD GLOW-WORMS AND THEin LIGHT. 189 



With the Tjampijridae are associated a few, small, closely allied 

 families at present very insufficiently known and imperfectly charact- 

 erised, but which from our point of view are of peculiar interest, since 

 it is to this systematically doubtful position that some of the Siamese 

 species belong. 



In the Lampi/ridae, the luminous organs are situated in the 

 terminal or subterminal segments of the abdomen, and the light is 

 shown from the under suiface. In dead as well as in living specimens, 

 these luminous areas are usually evident by their whitish, opaque, 

 almost waxy appearance, in strong contrast with the generally dark 

 colour of the underside. Thougli usually present to a greater or lesser 

 degree in both sexes, the luminous propert^^ is generall)" developed 

 much more liighly in one sex than in the other. When it is tlie male 

 beetle that possesses it in the greater degree, tlie light is shown when 

 the insect is on the wing, and is generally of an intermittent or 

 flashing character, and gives to the insects their popular name of 

 Fireflies. 



On the other har.d, when the power of luminositj^ is the more 

 highly developed in the female beetle, the character is usually associ- 

 ated with a more or less complete absence of wings, and the insect be- 

 comes nierelj'" a crawling, unpleasant-looking, worm-like creature, 

 generally known in fact as a Glow-worn), which nobodj' who is not an 

 entomologist would ever di-eam of calling a Beetle. The males of 

 these insects are winged, in form closely resembling the Fireflies, and 

 are totally unlike their spouses. The consequence of this utter dis- 

 similarity between the two sexes of one species is, that it is not easy 

 to co-relate them properly in our collections. Very often we have 

 large numbers of the males ot a species, even of whole groups of 

 species or genera, and j-et not a single female that we can say definite- 

 ly belongs to this species or to that. On the other hand we have a 

 considerable number of females of many different species which we are 

 unable at present to assign to their respective males. Some females, 

 for example, that Mr. Gairdner brought home are of great interest as 

 being diff'erentl}' constructed from females of normal Lampi/ridae : 

 evidently they belong to one of the small closely allied families refer- 

 red to above, but to which species or even genus they should be as- 

 signed cannot be determined without a knowledge of the male. We 

 liave also in the British Museum collection some larvae from Siam, 



