BRITISH INSECTS 



993 



group of Marine 

 Worms, this biol- 

 ogist holds that 

 brilhant pigment- 

 ary colours are 

 the cattse of the 

 unpalatability of 

 certain species, 

 and that there- 

 fore they can- 

 not have been 

 evolved as an 

 advertisement of 

 that unpalatabil- 

 ity, though they 

 may, in time, 

 have come to act 

 as an advertise- 

 ment. It is con- 

 ceivable that not 

 only pigmentary 

 colours (orange, 

 brown and black 

 mostly) but also 

 structural colours 

 (metalhc blues 

 and greens 

 mostly) may 

 have their origin 

 in some form of 

 excretion, and on 

 this ground Dr. 



Eisig's emendation of the original theory 

 has gained considerable support. 



One thing seems indisputable — that non- 

 sexual brilliancy of insect colouring, what- 

 ever purpose it may be serving at the 

 present, must have long since disappeared 

 if it had not served some definite purpose 

 in the past. This being so, we can, what- 

 ever be our opinions as to the exact 

 meaning of non-sexual brilliance, admire 

 without misgiving the fascinating theory 

 of " protective mimicry." It is unfor- 

 tunate that in natural history the word 

 'mimicry" should have acquired a re- 

 stricted meaning. It is a word which 

 has no convenient synonym, and whose 

 connotation should have been left wide. 

 It might have embraced, to the con- 

 venience of reader and writer alike, all 

 such natural simulations and dissimula- 

 tions, special and general, constant and 

 variable, as enable hving organisms to 

 appear to be what they are not. 



" Protective " mimicry, however, was the 



126 



TWO EXAMPLES OF PROTECTIVE MIMICRY IN THE 

 FORM OF EYE-MARKINGS, 



1. The female Emperor Moth. 2. The Caterpillar of the Large 

 Elephant Hawk-Moth. The latter when alarmed retracts 

 the front segments which carry the true eyes, and assumes 

 the terrifying appearance seen in the picture. 



term employed 

 by Bates in his 

 classical paper 

 contributed t o 

 the Linnean So- 

 ciety's transac- 

 tions in 1862, to 

 denote such sim- 

 ulations of shape 

 and colour as 

 enable a harm- 

 less unprotected 

 form of life to 

 derive advantage 

 in the struggle 

 for existence 

 from its resem- 

 blance to a 

 harmful or pro- 

 tected form. 

 Strictly speaking, 

 then, "protective 

 mimicry " is a 

 highly specialised 

 branch of that 

 protective resem- 

 blance to sur- 

 roundings which 

 influences the 

 whole existence 

 of the lower 

 orders, and which 

 forms their most powerful weapon. 



In the same way " aggressive mimicr\' " 

 is a highly specialised branch of what is 

 termed " aggressive resemblance." For a 

 full understanding of the modern classi- 

 fication of protective and aggressive 

 resemblances in Nature I must refer the 

 reader to such a book as Poulton's " The 

 Colours of Animals," and I must content 

 myself here with a brief resume of this 

 classification, and with a few comments 

 on the photographs which I have selected 

 as illustrations of it. It should perhaps 

 be pointed out that, as far as protective 

 or aggressive resemblance is concerned, 

 it is of the essence of a good photograph 

 that it should be something in the nature 

 of a puzzle picture. Professor Poulton 

 defines protective resemblance as " con- 

 cealment as a protection against enemies," 

 and subdivides it into general and sjiecial 

 protectiv^e resemblance. The former is 

 a colour i)rotection only, while, in 

 the latter, form as well as colour are 



