130 ORGANIC EVOLUTION 



Warning colors. 



Warning colors are another important class. Many ani- 

 mals are dangerous because of some means of defence, or are 

 noxious or nauseous as food, and many such are conspic- 

 uously colored, as if advertising their dangerous or disagree- 

 able nature. Many insects show conspicuous colors of this 

 sort. Many of the bees, wasps, hornets, and yellow-jackets 

 are conspicuously banded with yellow or white, or have a 

 brilliant metallic lustre, like the blue wasps (Plate 74). 

 That this conspicuous coloration is an actual protection to 

 these stinging insects is readily shown by experiment. Very 

 few insect-eating birds, lizards, frogs, toads, or mammals will 

 eat these insects. Apparently they have learned that they 

 are unpalatable. By experimenting with young birds which 

 have never before seen bees or wasps we get evidence that 

 the noxious character of the insect has to be learned, but it 

 is learned with astonishing rapidity, and when once learned, 

 seems not to be forgotten. Lloyd Morgan describes feed- 

 ing a young chick with flies among which he placed a 

 wasp. The chick took the wasp, was stung, and sho\ved 

 great agitation, wiping its bill and scratching it. Several 

 days later, while again feeding the little fellow with flies, he 

 offered it another wasp. The chick looked at the wasp, 

 turned away from it, and began wiping its bill, apparently 

 remembering the disagreeable sensations which followed its 

 former attempt to eat a wasp. Hundreds of experiments 

 show a similar ability in other birds, in lizards, frogs, toads, 

 and monkeys, to rapidly learn the unpalatable character of 

 conspicuous insects. If the stinging Hymenoptera * were 

 less conspicuously colored, they would often be mistaken 

 for edible forms and either be eaten or at least be grasped 



1 Ants, bees, and wasps. 



