4 MY LIFE [Chap. 



have a similar protection. I had just ascertained from Mr. 

 Jenner Weir that one of our common white moths (Spilosoma 

 menthrastri) would not be eaten by most of the small birds 

 in his aviary, nor by young turkeys. Now, as a white moth 

 is as conspicuous in the dusk as a coloured caterpillar in the 

 daylight, this case seemed to me so much on a par with the 

 other that I felt almost sure my explanation would turn out 

 correct. I at once wrote to Mr. Darwin to this effect, and 

 his reply, dated February 26, is as follows : — 



"My Dear Wallace, 



" Bates was quite right ; you are the man to apply 

 to in a difficulty. I never heard anything more ingenious 

 than your suggestion, and I hope you may be able to prove 

 it true. That is a splendid fact about the white moths ; it 

 warms one's very blood to see a theory thus almost proved to 

 be true." 



The following week I brought the subject to the notice of 

 the Fellows of the Entomological Society at their evening 

 meeting (March 4), requesting that any of them who had 

 the opportunity would make observations or experiments 

 during the summer in accordance with Mr. Darwin's sug- 

 gestion. I also wrote a letter to The Field newspaper, 

 which, as it explains my hypothesis in simple language, I here 

 give entire : — 



"Caterpillars and Birds. 

 " Sir, 



"May I be permitted to ask the co-operation of 

 your readers in making some observations during the coming 

 spring and summer which are of great interest to Mr. Darwin 

 and myself ? I will first state what observations are wanted, 

 and then explain briefly why they are wanted. A number 

 of our smaller birds devour quantities of caterpillars, but there 

 is reason to suspect that they do not eat all alike. Now we 

 want direct evidence as to which species they eat and which 



