272 Mr. C. F. M. Swyiinerton on the 



one half of what it lost when their colour-patterns were 

 diflferent. This is, of course, what is known as " MuUerian 

 mimicry/' '' common warning colours/' or " synapose- 

 matism." 



I have myself made a point of testing very fully indeed 

 the validity of both theories. I found, in common with 

 previous experimenters, that Bates was right in supposing 

 that some species are pleasant and others unpleasant (it is 

 a matter of relative digestibility rather than of '^ uupal- 

 atahility ■"). But I also found — as Marshall had begun to 

 find — that there were numerous degrees of unpleasantness. 

 This at once extends Bates'* principle even to the class 

 of resemblance — that between unpleasant species — which 

 had so puzzled him. I found moreover that Miiller 

 was wrong in supposing that after a certain number 

 of tastings, approximately the same for each different 

 appearance, young birds refrain from attack on un- 

 pleasant prey. Birds go on all their lives eating such 

 prey whenever hungry enough — it may be several times a 

 day — and, moreover, they go on all their lives making 

 mistaken attacks, though these mistakes are less frequent 

 apparently in the case of prey that they have frequeutly 

 and recently met with. 



From this last, it would seem to be true enough that an 

 abundant species may be less persecuted than a scarce one 

 with a different colour-pattern. But this comes about not 

 in virtue of its incurring the same absolute loss as the other, 

 as Miiller supposed, but through a quite different principle — 

 greater reminding-power and far less attack. 



In this case, again, it may pay two species with the same 

 unpleasant qualities to possess a colour-link in common, 

 not in order to share between them a fixed and other- 

 wise irreducible loss, but for greater reminding-power and 

 facilitated recognition generally, resulting in lessened 

 attack. This is " synaposematism ''' as it probably actually 

 exists. 



To sum up : (1) A pleasant species may mimic an un- 

 pleasant species and so share in its relative immunity from 



