1887.] VALUE OF COLOUR AND iMAKKlNGS IN INSECTS. 227 



advantage, that they only include insects which have been sub- 

 jected to actual experiment. Although the tables comprise so few 

 instances, I think that the resemblances of colour and pattern are 

 most remarkable, and hard to explain under any other theory. My 

 suggestion does at any rate point out a very obvious use for the 

 resemblances. The advantages which every conspicuous and nauseous 

 or dangerous species would gain by setting as simple a lesson as 

 possible to the foes of its class, would be so great that there is no 

 difficulty whatever in the supposition that every stage towards con- 

 vergence in colours and in patterns would have been beneficial, 

 and, as such, would have come under the influence of natural 

 selection. It is to be noted that advantage would accrue in the 

 greater thoroughness of the education, no less than by shortening 

 the process ; for a few colours, with a few simple patterns scattered 

 over a number of species, would be remembered more easily than a 

 larger number with a separate pattern in nearly every species. 



I am aware that this suggestion is but an extension to the whole 

 group of conspicuous insects of the explanation offered by Pritz 

 Mvilier to a fact which seemed for a long time an inexplicable 

 difficulty, the undoubted fact that conspicuous butterflies presumably 

 protected in the most complete manner by nauseous attributes, 

 nevertheless mimic each other in the most unmistakable way. Bates, 

 the original discoverer of " mimicry " in the animal kingdom, pointed 

 out these apparently mj'sterious resemblances in the paper in which 

 "mimicry" was itself explained and illustrated. Wallace looked 

 upon these obscure similarities between protected forms as due to 

 some unknown cause connected with locality. 



It remained for Dr. Fritz Mliller to explain the difficulties in a 

 paper entitled " Ituna and Thyridia; a remarkable case of Mimicry 

 in Butterflies " (' Kosnios,' May 1879, p. 100). Arguing from the 

 instance of these two genera, which both belong to protected groups 

 and which resemble each other, Dr. Miiller suggested that under 

 these circumstances an advantage would be gained by each of them, 

 because the number of species which must be sacrificed to the 

 inexperience of young birds and other enemies would be made up 

 by both of them instead of by each independently. This paper was 

 translated by Prof. Meldola, and appeared in the ' Proc. Ent. Soc. 

 Lond.' (1879, p. xx). In a subsequent paper by Dr. Miiller 

 (' Kosmos,' V. Jahrgang, 1881), the same subject is considered in 

 greater detail, and the results are accepted and expounded by Wallace 

 in ' Nature ' (vol. xxvi. p. 86). The mathematical aspect of the 

 subject was, however, inaccurately stated in this last paper, the correct 

 statement being supplied by Mr. Blakiston and Mr. Alexander of 

 Tokio, Japan ; the correction being published in letters by Mr. 

 Wallace and Prof. Meldola to 'Nature' (vol. xxvii. p. 481). 

 Subsequently a letter appeared in ' Nature' (vol. xxix. p. 405) from 

 Mr. Blakiston and Mr. Alexander, giving the complete mathematical 

 statement of the advantages gained by each of the protected species. 

 The law is given in these words, " Let there be two species of insects 

 equally distasteful to young birds, and let it be supposed that the 



