436 Mr. G. A. K. Marshall on 



existence is far keener in the dry winter season, and that 

 butterflies arc especially subject to it. 



The most distasteful forms, many of which are the 

 models for mimicry, are sufficiently protected to retain 

 their conspicuous aposematic appearance throughout the 

 year, and either exhibit no change in the winter season or 

 a change which is not in any way cryptic. 



While this is true of all the larger and most conspicuous 

 Acra^as, some of the smaller Acrseas do exhibit changes 

 in a cryptic direction in their winter generations. These 

 are Acra^as which, from their colouring and habits, may 

 be inferred to possess only a moderate degree of unpalat- 

 ability as compared with the other species of the genus. 



Cases in which colouring is " warning and protective 

 [procryptic] at the same time " are quite common, e. g. 

 the protected larvte of many Tentltrcdinidx which har- 

 monize sufficiently well with their food-plant to be con- 

 cealed at a little distance, but assume the most conspicu- 

 ous aposematic attitudes and movements as soon as they 

 are discovered and disturbed. But in the case of the 

 smaller Acraias suggested by Mr. Marshall, the colouring 

 which is most procryptic does not occur at the same time 

 as that which is less procryptic or probably aposematic. 

 Mr. Marshall's numerous experiments upon the edibility of 

 the smaller Acrteas (see Sections 9, 18, 19) do not support 

 the view that any of them are palatable to the insect- 

 eating animals made use of. It has already been pointed 

 out that the refusal or evident dislike of insect food by 

 captive animals is trustworthy evidence of unpalatability, 

 while acceptance is not proof of palatability (see p. 317). 

 The smaller Acraeas furthermore fall into beautiful s}ti- 

 aposematic groups (see pp. 492, 493) ; indeed a strong 

 Mlillerian association can be recognized throughout almost 

 the whole of the Ethiopian representatives of the genus, 

 as was first suggested by Professor Meldola (Ann. and 

 Mag. Nat. Hist., ser. 5, vol. x, 1882, p. 425). 



It is therefore probable that these smaller Acraeas are 

 still specially protected, although to a less extent than 

 other species of the genus, but that the keener struggle 

 of the dry season has compelled them to produce gener- 

 ations which are inconspicuous as compared with those of 

 the wet season. 



If these interpretations here suggested be correct, the 

 parallelism with Precis sesamus, etc., is very remarkable. 



