174 TEOPICAL NATURE, AND OTHER ESSAYS. 



beautiful caterpillar of the emperor-motli, whicli is 

 green with pink star-like spots, to be protectively 

 coloured ; yet, when feeding on the heather, it so har- 

 monises with the foliage and flowers as to be almost 

 invisible. Every day fresh cases of protective colouring 

 are being discovered, even in our own country ; and it is 

 becoming more and more evident that the need of pro- 

 tection has played a very important part in determining 

 the actual coloration of animals. 



Warning Colours. — The second class — the warning 

 colours — are exceedingly interesting, because the object 

 and effect of these is, not to conceal the object, but to 

 make it conspicuous. To these creatures it is useful to 

 be seen and recognized ; the reason being that they have 

 a means of defence which, if known, will prevent their 

 enemies from attacking them, though it is generally 

 not suflicient to save their lives if they are actually 

 attacked. The best examples of these specially pro- 

 tected creatures consist of two extensive families of 

 butterflies, the Danaidse and Acrseidae, comprising many 

 hundreds of species inhabiting the tropics of all parts of 

 the world. These insects are generally large, are all con- 

 spicuously and often most gorgeously coloured, present- 

 ing almost every conceivable tint and pattern ; they all 

 fly slowly, and they never attempt to conceal themselves ; 

 yet no bird, spider, lizard, or monkey (all of which eat 

 other butterflies) ever touches them. The reason simply 

 is that they are not fit to eat, their juices having a 

 powerful odour and taste that is absolutely disgusting to 

 all these animals. Now we see the reason of their 

 showy colours and slow flight. It is good for them to 

 be seen and recognised, for then they are never mo- 



