iv SHIFTS FOR A LIVING 59 



f 



the protective resemblance has been definitely proved. 

 Thus Cesnola tethered Mantises of the green variety on 

 green plants and others of the brown variety on brown 

 plants, and conversely, and found that the birds picked 

 off the green insects on the brown background, the brown 

 insects on the green background, but failed to detect 

 green on green or brown on brown. This is a good in- 

 stance of the experimental verification of the operation 

 of natural selection. 



8. Warning Colours. While many animals are con- 

 cealed by their colouring, others are made the more 

 conspicuous. But, as the latter are often unpalatable or 

 dangerous, Wallace suggested that the colours were 



FIG. 13. Moss INSECT. 

 (From Belt.) 



warnings, which, as Poulton says, ' assist the education 

 of enemies, enabling them to easily learn and remember 

 the animals which are to be avoided." Expressing the 

 same idea, Belt says, " the skunk goes leisurely along, 

 holding up his white tail as a danger-flag for none to 

 come within range of his nauseous artillery." So, the 

 brightness of the venomous coral-snake (Elaps) is a 

 warning ; the rattlesnake, excitedly shaking its rattle, 

 " warns an intruder of its presence " ; the cobra ' en- 

 deavours to terrify its enemy by the startling appearance 

 of its expanded hood and conspicuous eye-like marks." 

 The language in which conspicuous colours are described 

 by many naturalists tends to exaggerate the subtlety 

 of animals, for the intentional warning of possible moles- 



