238 THE COLOURATION OF INSECTS 



In 1915, while on active service in German East Africa, 

 I saw two wagtails at puddles eat eleven butterflies in 

 five minutes, and on another occasion saw one eat eleven 

 butterflies in three minutes, definitely selecting for its 

 food Lycaenidae, Belenois, Atella, from among a crowd 

 of butterflies assembled on the mud, and paying no atten- 

 tion to a number of the typically aposematic Danaine 

 Amauris echeria, or the black and scarlet Papilio 

 ridleyanus, mimetic of Acraea egina.^ 



Lastly, it may be said, when dwelling on this question 

 whether birds do or do not by eating butterflies cause 

 mimetic resemblances, is it not too often forgotten that 

 butterflies are not the only mimics ? No one will deny 

 that spiders are eaten by birds, or flies, or beetles, or 

 grasshoppers, yet numbers of mimetic members of all 

 these groups are known, all explicable by the same theory 

 as mimicry among butterflies, and all must stand or fall 

 together. 



Dr. W. H. Longley has suggested a modification of 

 Thayer's views on concealment, supposing that all 

 species have been forced to assume colour combinations 

 which most effectually conceal them in their normal en- 

 vironment ; and that in a few cases patterns have appeared 

 which have been sufficiently alike to deceive enemies 

 which discriminate in their choice of food.^ This hypo- 

 thesis thus evades the difficulty of understanding the 

 gradual building up of a mimetic likeness while acknow- 

 ledging that mimicry does exist and is of value to the 

 mimic, and that different degrees of edibility exist, but 

 it affords no explanation of the difference in behaviour 

 between model and mimic. If both Planema tellus and 

 Pseudacraea eurytus form terra, are equally well concealed, 

 why should the former be so bold that it can be plucked 



^ Proc. Ent. Soc, 1915, pp. Ixix.-lxxv. 



'^ " A Revised Working Hypothesis of Mimicry," The American Natural- 

 ist, vol. li, May 1917, p. 276. 



