6 MY LIFE 



alone; because if birds could not bell the eatable from the 

 uneatable till they had Beized and tasted them, the protection 

 would be of no avail, a growing caterpillar being so delicate 

 thai a wound is certain death. If, therefore, the eatable cater 

 pillars derive a partial protection from their obscure and 



imitative colouring, then we can understand that it would hi' 



an advantage to the uneatable kinds to be well distinguished 



from them by bright and conspicuous colours. 



" I may add that this question has an important bearing on 

 the whole theory of the origin of the colours of animals, and 

 especially of insects. I hope many of your readers may be 

 thereby induced to make such observations as I have indicated, 

 and if they will kindly send me their notes at the end of the 

 summer, or earlier, I will undertake to compare and tabulate 

 the whole, and to make known the results, whether they con- 

 firm or refute the theory here indicated. 



" Alfred R. Wallace." 



"9 St. Mark's Crescent, Regent's Park, N.W., 

 March, 1867. 



This letter brought me only one reply, from a gentleman 

 in Cumberland, who informed me that the common " goose- 

 berry " caterpillar, which is the larva of the magpie moth 

 (Alfraxus grossalariata) , is refused by young pheasants, par- 

 tridges, and wild ducks, as well as sparrows and finches, and 

 that all birds to whom he offered it rejected it with evident 

 dread and abhorrence. But in 1869 two entomologists, Mr. 

 Jenner Weir and Mr. A. G. Butler, gave an account of their 

 two seasons' experiments and observations with several of 

 our most gaily-coloured caterpillars, and with a considerable 

 variety of birds, and also with lizards, frogs, and spiders, con- 

 firming my explanation in a most remarkable manner. An 

 account of these experiments is given in the second and all 

 later editions of my book on " Natural Selection " ; but it 

 is more fully treated in my " Darwinism, " chap. ix ? under the 

 heading ' Warning Colours among Insects," and it has thus 

 led to the establishment of a general principle which is very 

 widely applicable, and serves to explain a not inconsiderable 



