TRUE MIMICRY 



115 



this species. Seitz was so much surprised by the discovery that the 

 male, which had quickly detached itself from the female, escaped 

 him, and he could only make out that, 'as it flew away, it unfolded 

 dark wings, which certainly bore little resemblance to those of the 

 lemon butterfly.' In the hope of securing more of this rare bootv he 

 then hunted only for Catopdlia argante, without however securing 

 another coveted specimen — he caught no more Ancece, which shows 

 that in this case, too, the mimetic species was much rarer. 



We see, then, that the need for protection in butterflies lias 

 a great influence on their external appearance, especially as regards 

 their colour and marking. First, because the resting insect frequently 

 has the visible surfaces sympathetically coloured, and also, because 

 there are numerous species, indeed whole families, which contain 

 nauseous, perhaps even actually poisonous, juices, and these have been 

 subject to a double process of selection, directed towards the increase 

 of the nauseousness, and at the same time towards acquiring as 

 conspicuous a dress as possible. Thus the whole surface of these 

 butterflies became gaily coloured, and often — as in many of the 

 tropical nocturnal Lepidoptera which fly by day, the Agaristidae, 

 Euschemidre, and Glaucopidae — quite glaringly bright. We thus 

 understand the striking or at least readily recognizable colours of 

 the Heliconiidaa, the Euplceae, the Danaidae, and the AciTeidae. 

 Finally, the unpalatable species influence many others which are 

 edible, since the latter strive to resemble an immune species ; and how 

 considerable the variations and colour transformations thus induced 

 can be is shown by the Whites of the genus Perhybris (PL II, Figs. 16 

 and 17) and Arclionias, in which the male has wholly or partially 

 retained the primitive dress of the Whites, and in which, side by side 

 with wholly mimetic species, other species occur in which both sexes 

 exhibit the garb of the Whites unaltered. Such cases tell decidedly 

 against the often expressed view that mimetic species must have had 

 from the outset a great resemblance to the model ; they show rather 

 that very great deviations in form, but more especially in colour, have 

 been brought about solely by the necessity for mimetic adaptation, and 

 that the}^ have come about only slowly and step by step, as the 

 different grades of resemblance to the model in different species of 

 the same genus clearly show. 



Lepidoptera are by no means the only insects which exhibit the 

 phenomenon of mimicry, nor are insects the only animals in which it 

 occurs; and unpleasant taste and odour are not the only protective 

 characters ; there are many others, as, for instance, among insects, the 

 hardness of the chitinous cuticle. 



