356 THE PLACE OF MIMICRY 



species, leading it to resemble two or more models, 

 although at first sight suggesting only a Batesian inter- 

 pretation, does not by any means exclude the Miillerian. 

 The facts presented by a dominant well-protected 

 Acraeine mimic prove that a resemblance to more than 

 one model cannot serve as a criterion between the two 

 rival theories. 



14. A Possible Instance of Observable Change in 

 a Member of a Miillerian Group since 1825-7. A power- 

 ful combination 1 of distasteful butterflies in Eastern 

 Brazil has developed a characteristic pattern of which the 

 most marked feature is a bright yellow horizontal band 

 running along the hind wing. The central members are 

 Ithomiinae and Heliconinae. An outlying member is the 

 Danaine butterfly Lycorea halia, with a pale band instead 

 of a bright yellow one. In the Hope Collection at Oxford 

 there are eight examples, captured by W. J. Burchell, 

 in Brazil, between Nov. 10, 1825, and Dec. 24, 1827. 

 There can be no doubt that these specimens, which are 

 in very good condition, are on the whole further removed 

 from the combination than captures of recent date, ' inas- 

 much as the band is but slightly paler than the tawny 

 ground colour of the wing.' Unless, therefore, there has 

 been a darkening of tint with age, we have here an example 

 of approach towards the combination since 1825-7. The 

 case is precisely of the kind in which some observable 

 change might be looked for. That a butterfly which is 

 outlying to-day should have been even more outlying 

 seventy-five years ago, is not surprising. But many 

 further observations must be made before the evidence 

 can be accepted as in any way satisfactory. 2 



B. ALLAPOSEMATIC COLOURS, OR ADVENTITIOUS 

 WARNING COLOURS. 



Certain palatable animals make use of the Special 

 Defence and Warning Colours of other forms. Thus, 

 the common English hermit-crab, Pagurus bernhardus* , 



1 Blandford's Series iv, Group 3, Division (a) : see Proc. Ent. Soc., 

 Lend., 1897, p. xxiv. 



2 See Ann. Mag. Nat. Hist., ser. 7, vol. xiii, May 1904, pp. 359-60. 



