44 I'KOCKEDIXGS OF III K 



rcseiubliiii^ tlio iioii-iiiiiiielic nuile ( Fiij;. 2), and still more closely 

 tlie iion-iuiiiietie I'eiiKiIes of the Miulagascar /■'. menones. It ia 

 11 jtHwortliy tliat tlie triangular fore-wing patch shown in Fig. 12 

 is more dyslegnic than in any hippocoon, although Idppocooii itselt" 

 contrasts strongly with the eiilegnic model Amduris niavhis. 

 From Fig. 12 onwards towards Fig. 19 the amount of dyslegii'a 

 incnsases until the bar itself lias gone, being represented only by 

 a dusting of dark scales, of which a trace can still be detected in 

 Fig. 19. 



The results obtained by Dr. Lainborii, and here represented in 

 the plate, taken in conjunction witli Dr. Carpenter's researches 

 in the N.W. Victoria Nyaiiza and Mr. C. F. M. Swynnerton's 

 in 8.E. lihodesia, offer very strong evidence that the con- 

 stancy of the iiiimetic forms which have been the subjects of 

 investigation is due to the operation of natural selection in the 

 presence of the approi)riate models, and that when such models 

 are scarce or absent the constancy is no longer maintained on the 

 same level. It is furthermore important that Dr. Carpenter has 

 observed that variations such as those shown in the oblique fore- 

 wing bar of dion)/sus are quite conspicuous on the wing* ; and if 

 they are such as to constitute departures from the pattern of the 

 model, there is no reason for believing that the difference is less 

 evident to the eyes of their natural enemies. 



G. The Beginning or Mimicry: tue F'ikst Step. 



Alluding to the resemblance of Chalcosiine moths of the genera 

 Amesia and Callamesia to the dark blue-shot Euplceas of India, &c., 

 I wrote in 1890 t: — " There are also examples which show us the 

 origin of mimicry — examples in which the resemblance is very 

 imperfect, but, nevertheless, sufHcient to afford some protection, 

 .... It is extremel)^ probable that the wonderfully close likeness 

 of many mimetic species arose by gradual stages from a general 

 resemblance to a type of colour or pattern possessed by a large 

 group of unpalatable insects." In 1912 I discussed % the origin 

 of the mimetic Uganda female of Acrcea ah-io/ie^ which resembles 

 the male of Flanema macarista and the male and female of 

 P. po(j(/ei. I gave reasons for the belief that the resemblance 

 to these Uganda models was started by the sudden appearance of 

 a white bar crossing the hind wing. It was also shown that 

 variations of this kind do arise ; for out of 294 S. Nigerian 

 females bred by j\Ir. W. A. Lamborn, a single one exhibited a 

 well-marked white bar crossing the fore w ing, thus showing " how 

 a mimetic moditication might arise if an appropriate model existed 



* Bedrock, Oct. 1913. pp. 3(10, 361 ; Apr. 1914, pp. 34, 35. 



+ Nature, Oct. 2. Reprinted in " Essays on Evolution," Oxford, 1908, 

 p. 370. 



t IScfhnck, April 1912. p. 48; quoted in Bcfhock, Oct. 1913, pp. 301, 302, 

 which should also be cousulted, together with the No. for Apr. 1914, p. 45. 



