MIMETIC ANALOGY. 45 



by certain writers, who imagine that the words imply that 

 the animals have power to change or alter their own condi- 

 tion. No supposition can be possibly more absurd. The 

 change is not effected by the will of the individual animal, 

 but occurs in the species ; variations are involuntary, and at 

 present even their very cause is unknown ; all that is known 

 is that they do occur both in wild and domestic animals, and 

 that they are capable of hereditary transmission." 



This imitation of natural objects is not confined to a few 

 species ; but has been observed in entire groups, and even in 

 the whole insect fauna of a country at particular seasons. 

 The Rev. Joseph Greene, writing on our autumnal and winter 

 moths in the Zoologist for 1856, says: "I am not aware 

 whether any entomologist has ever been struck by the singular 

 adaptation and similarity of colouring in the autumnal and 

 winter Lepidoptera to the prevailing tints of nature during 

 these seasons. Counting from the middle of September, when 

 the leaves begin to turn, to the end of February, we find 

 among the Bombyces, Noctuse, and Geometra?, about fifty- 

 eight species on the wing. Now in the autumn the hue of 

 nature is golden she passes through all the intermediate 

 stages from pale yellow to a deep rich brown ; while in 

 winter s]je assumes a grey or silvery garb. Taking those 

 fifty-eight species, we find in their prevailing colours a striking 

 and remarkable similarity to those which nature assumes at 

 the time of their appearance in a winged state. Three species 

 are doubtful, seven militate against my theory, the remainder 

 are decidedly in my favour." He then proceeds to enume- 

 rate the autumnal species, which are yellow or rich brown, 

 and the winter species, which are grey or silvery, and con- 

 cludes : " It certainly strikes me as a very interesting fact, 

 showing the hand of an Almighty and Allwise Being to be 

 visible in this as in all the other works of the Creation." 



These imitations are not confined to tl\e invertebrate 

 animals or the loAver forms of life, for there are examples of 

 mimetic analogy among the warm-blooded vertebrata. Thus 

 the grey-banded cuckoos so closely resemble hawks, both in 

 appearance and flight, that they are constantly mistaken for 



