THE GLOWWORM 49 



Some naturalists seem to think that an explanation which 

 suits only one species cannot be the true one. It seems 

 to me that we complicate the problem unnecessarily by 

 seeking for an explanation which will apply to all luminous 

 insects, or even to all the Lampyridae, some fifty in number. 

 Why not consider the species one by one, and so eliminate 

 the perplexing differences in habits and environment which 

 always exist among a number of different species ? We 

 have no ground for supposing that the explanation which 

 suits one case will suit all. The sounds and colours of 

 animals admit of no universal explanation, and the same 

 is likely to be true of luminosity. I would therefore prefer 

 to consider the English glowworm by itself, not of course 

 neglecting any pertinent suggestions which might be 

 drawn from other species, but not waiting till they come 

 to hand. 



One speculation which has found eminent adherents is 

 this. The glowworm has been thought to have a dis- 

 agreeable taste which repels night-feeding animals, such 

 as bats, and it is quite true that when a number of glow- 

 worms are imprisoned in a small vessel an unpleasant 

 odour can be detected. The light, it is said, may be a 

 warning light, giving notice that the insect is one which 

 is notoriously ill-tasted. Belt put forth this view, and 

 Darwin l supported it. Bongardt has pointed out that 

 the taste and smell of the glowworm do not repel spiders, 

 which prey upon it freely, but this argument is of course 

 not decisive. Belt's explanation seems to me to fail in 

 dealing with such material facts as the great eyes of the 

 winged male, the ostentatious self-exposure of the wing- 

 less female, and the recently acquired knowledge that 

 when the males gather about the female she emits a 

 brighter light. Besides, if the female were luminous for 

 self-protection only, if would suffice if she were luminous 

 in a low degree, so as to prevent mistakes on the part of 

 insectivorous animals within striking distance ; self-pro- 



1 Descent of Man, chap. x. 



D 



