THE MOTH AND THE CANDLE 235 



another, but to scare would-be predatory foes, such as 

 birds, bats, and reptiles. I have heard a story (which 

 I should like to have confirmed) that in some part of 

 tropical Asia a certain kind of bird collects half a dozen 

 or so of a species of glow-worm and places them at the 

 entrance to its nest, so as to scare nocturnal animals 

 which might attack its eggs or its young. It is a note- 

 worthy fact that a point of light in the dark may act in 

 two opposite ways on animals which see it either it 

 attracts or it repels them. The physiologist calls this 

 positive and negative " photo-taxis " (light-guidance). 

 And we have the similarly positive and negative in- 

 fluence of chemical taste and smell, called " chemo-taxis," 

 and a similarly contrasted positive and negative " hygro- 

 taxis," or directive influence of moisture upon the move- 

 ments of animals and plants. 



