22 PHYSIOLOGICAL CLASSIFICATION 



tropical tree lizard Calotes will take its stand 

 beside a beehive to catch the bees as they issue, 

 swallowing them entire ; ! or beside an incipient 

 termite mound picking off the workers. Bulbuls 

 will gather round a swarming termite nest and 

 decimate the winged emigrants. Bats will fly to 

 a bright light, not because they are themselves 

 attracted by it, but because they know where to 

 find insects, especially winged termites, which are. 

 Geckoes and toads similarly approach artificial 

 light in search of insect food. In the three 

 last-mentioned examples of nocturnal animals 

 seeking their food by artificial light we find 

 once more (as in the case of moths) positive 

 phototaxis in apparent conflict with negative 

 heliotropism. 



It seems important to take notice of this 

 association of contrary reflexes, of which more 

 instances will be found below. Meanwhile it 

 may be useful to distinguish habits from re- 

 actions : — a habit is the behaviour of an animal 

 in the open ; a reaction is its behaviour in 

 the laboratory. Finally, whilst dealing with 

 definitions we may add that the word tropism 

 means the tendency to react in a definite manner 

 towards external stimuli. 



1 Mr Francis Buckland has recorded a similar observation of the 

 common toad eating bees in Oxfordshire. 



