to limitations of the Mullerian Hypothesis of Mimicry. 135 



With regard to the black, white-spotted area at the 

 base of the under-side of the hind-wing in the wet phase 

 of sesamus and antilope, Professor Poulton has himself 

 recognised that this marking is not so isolated as he at 

 first thought (p. 427). Indeed, it actually occurs in those 

 very Acrseas to which these insects present a rough 

 mimetic resemblance, and therefore its appearance in 

 Freds can quite consistently be explained on Batesian 

 lines. Thus an important plank in his argument 

 collapses. 



Next as to the case of jjdasyis, Professor Poulton says 

 that "the conspicuous appearance of the under-sides of 

 these forms is doubtless chiefly adapted to render them 

 conspicuous during the attitude of rest" (p. 438). Now 

 unlike Danaines and Acrseas, I have found it no easy 

 matter to discover a wet-phase Precis in an attitude of 

 prolonged rest, and in every such case that I can recollect 

 the butterfly had concealed itself on the under-surface of 

 a leaf; a position which can hardly be considered to lend 

 itself to a display of warning colours. 



During my last summer in Rhodesia I kept a special 

 look-out for pelasgis, and on three occasions 1 observed a 

 specimen going to roost under the broad leaves of its food- 

 plant. I trust some other entomologist will check my 

 observations, for I must confess that I utterly failed to 

 detect in the appearance of these insects anything which 

 could be described, even by the widest stretch of imagin- 

 ation, as " startlingly conspicuous " (p. 429). On the 

 contrary, the general effect of the colouring harmonised 

 with the surroundings in a way one would not expect 

 when merely examining the insect in the cabinet ; for the 

 pale transverse stripe (the so-called " warning " band) did 

 not throw the insect into relief, but served only to break 

 up its contour, which thus became less obvious in the 

 lights and shadows among the leaves. I do not wish to 

 maintain, however, that the colour of pelasgis is ideally 

 procryptic; far from it. But of this I feel assured, that 

 it would atford adequate protection to an edible species at 

 a time when the struggle for existence is not too keen, 

 and when the shrubs and bushes still retain sufficient 

 leaves beneath which it may safely shelter. Nor can I 

 think that its colouring would prove a danger to so alert 

 and active an insect durinof its waking hours. 



The next point to be considered is the supposition that 



