442 



SCIENCE. 



[N. S. Vol. VII. No. 170. 



possesses merely a trace of the wide black 

 bar that in two other forms divides the pale 

 ground color into perfectly separate sub- 

 apical and inner marginal spaces in the 

 fore wings, and the hind wings are ochre- 

 yellow with a narrow black border.* Pro- 

 fessor Poulton has. however, kindly shown 

 me, in the Hope Collection of the Oxford 

 University Museum, a much closer approx- 

 imation to the masculine coloration in an 

 extraordinary example of the female P. 

 cenea from Zanzibar. In this female the 

 transverse trace of black in the fore wings 

 is even fainter than in the dionysos form, 

 and the color of the wide pale spaces and 

 hind marginal spots in all the wings is almost 

 exactly of the pale creamy-yellowish tint 

 of the male P. cenea ; and on the under side, 

 while the pale-yellowish of the fore wings 

 is better divided by blackish than on the 

 upper side, the coloring of the hind wings 

 corresponds much more nearly to that of 

 male than in any other female I have seen — 

 the characteristic break in the submarginal 

 brownish band being moreover very com- 

 plete and wide. There can be no doubt 

 that in this specimen we have a marked 

 case of reversion to the original coloring of 

 the female, but it is unaccompanied by any 

 inclination towards the recovery of the lost 

 tail of the hind wings. 



Returning to the general aspects of the 

 subject, it is of importance to consider more 

 closely how the evidence stands in relation 

 to (a) persecution by insectivorous foes; 

 (b) possession of malodorous and distaste- 

 ful juices by certain groups; (e) rejection or 

 avoidance by foes of the insects provided 

 with offensive juices, and (d) loss occa- 

 sioned to distasteful species by the attacks 

 of young and inexperienced enemies ; for it 

 is admittedly on the cooperation of these 

 factors that the theory of mimicry depends. 



*Hemtson (Exot. Butt., IV., Papilio XII., fig. 39) 

 delineates an example in many respects intermediate 

 between dionysos and hipjmcoon, but rather closer to 

 the latter form as regards the fore wings. 



(a) As regards the first point, the broad 

 fact of insects generally constituting the 

 food of countless devourers, vertebrate and 

 invertebrate, is beyond dispute; immense 

 and incessant persecution is universally at 

 work. But when we proceed to examine 

 this world-wide persecution more in detail, 

 and to ask in what special directions it 

 works, or what groups or species are the 

 particular prey of certain groups or species 

 of enemies, we very soon discover how 

 little is exactly known. Birds, for instance, 

 are such notorious and apparently indis- 

 criminate insect-eaters, and some of them 

 are so active and demonstrative in their 

 hunting, that it seems but reasonable to 

 regard them as the chtef pursuers on the 

 wing of the abundant and defenceless but- 

 terflies. Yet in the discussion which fol- 

 lowed the reading of Dr. Dixey's last paper, 

 above referred to, nothing was more notice- 

 able than the very scanty testimony to such 

 persecution on the part of birds that could 

 be brought forward by the very competent 

 well-travelled entomologists present. In 

 fact, the poverty of observed cases of such 

 attack has induced the opinion among some 

 entomologists that birds very rarely chase 

 butterflies at all, and the published expres- 

 sion of this view by Pryer, Skertchley, 

 Piepers and other experienced collectors 

 cannot be overlooked. But I am persuaded 

 that in this instance, as in so many others 

 where the life-history of animals is con- 

 cerned, the dearth of evidence is due to the 

 neglect of well-directed and sustained ob- 

 servation. Little can be gained by merely 

 noting such cases as happen to force them- 

 selves on the collector's attention; the col- 

 lector must resolutely set himself to search 

 out and keep watch upon what really takes 

 place. Considering that there is no record 

 of any naturalist's having seriously taken 

 up the investigation of this matter in the 

 field, I think that very much positive evi- 

 dence could hardly be expected, and that 



