46 SOME SOl'TII INDIAN INSECTS, ETC. [CHAP. IV. 



beetles is remarkably high, being estimated at practically ioo per 

 cent, of the energy used, there being almost no heat-rays or actinic 

 rays, whilst the light-value of the electric arc is only about ten per 

 cent, of the energy used and that of the sun only about thirty-five 

 per cent. Several other beetles besides the Lampyrida are known 

 to be luminous, at least occasionally, and undoubtedly many more 

 Indian insects will be found to be capable of emitting light. 

 Amongst those insects in which this phenomenon has hitherto 

 been noted, mostly outside of India, are various beetles {Carabidtz, 

 Paussidee, Staphylinidee, Tembrionida, Elaterida, Cerambycidae, Bup- 

 restidce, etc.), Ephemeridae, larvae of Lepidoptera and Diptera, and 

 Collembola, but some of these are perhaps luminous as the result of 

 disease, the luminosit) being due to the activity of bacteria and 

 not to the presence of true photogenic organs. The intermittent 

 flash of a flying glow-worm is perhaps a means of defence by 

 puzzling an enemy as to its whereabouts. There is also some evi- 

 dence that Lampyrid beetles are distasteful to nocturnal insectivo- 

 rous birds and bats, so that the light is perhaps a "warning" 

 signal. 



