THE CAUSE or MIMETIC EESEMBLANCE ETC. 571 



kinds happen to possess stings — that the central types in the 

 groups o£ butterflies belong to subfamilies which are more 

 abundant and even more unpalatable than the generality of their 

 order. It is, furthermore, a mere coincidence tbat such groups 

 are formed round the Danainae and Acrceince, wherever they occur 

 in all the warmer regions of the world, and in tropical America 

 also round the Ithomiincd{Neotropincs),^'\\\c\\ are closely related 

 to the former, and the HeliconincB, which are closely related to 

 the latter. 



No theory except natural selection explains why the number 

 of colours and patterns in the dominant groups of buLtei flies 

 mentioned above are so few in relation to the number of species, 

 as was pointed out by Prof. Meldola (Ann. & Mag. .Nat. Hist., 

 Dec. 1882). These colours and patterns have been recently 

 studied very carefully, especially in the Ithomiinee, by A. Gr. 

 Mayer (Bulletin of the Mus. of Comp. Zool. at Harvard Coll., 

 Feb. 1897, p. 169). Mayer shows that "the 200 spe^-ies of 

 Pajnlio in South America display 36 distinct colors, while the 450 

 species of Danaoid Heliconidce \_Itho?nu)ice'\ exhibit only 15. 

 Hence the numbers of the species and of the colors are almost in 

 inverse ratio in the two groups. This may be explained by the 

 fact, tbat the Danaoid HeliconidcB mimic one another, while the 



Papilios do not There is no lack of individual variability 



among the species oi ih.e Danaoid Heliconidce ; yet the species 

 as a whole vary but little from the two great types of color- 

 pattern represented by Melincea and Ithomia. In order to 

 account for this remarkable fact, I am forced to resort to Frilz 

 Midler's theory of mimicry " (I. c. p. 229). Again on page 225 

 Mayer remarks : " It is difficult to account for the remarkable 

 conservatism in respect to color-variations among the i/^e//co??/c?« 

 [here used, as in Bates's original paper, to include DanaincB, Itho- 

 miinee, and Seliconince'], unless we resort to the explanation 

 afforded by the theory of mimicry ; for, while there is such 

 remarkable simplicity and uniformity of color-pattern throughout 

 the whole group of the Heliconidce, individual variations ave very 

 common." 



It is not from any predisposition or bias in favour of natural 

 selection that these conclusions are reached, but simply because 

 natural selection ofl'ers an explanation of so many remarkable 

 facts which are utterly meaningless under any other theory yet 

 brought forward. 



