104 THE EVOLUTION THEORY 



which were originally directed towards concealment. According to 

 the beautiful observations of Erich Haase on this genus Elymnias, 

 the ground-colouring on the under surface must have been 'a grey, 

 darkly mottled protective one/ as still occurs, for instance, in several 

 mimetic species, such as Elymnias lais (PI. II, Fig. 30). This leaf- 

 colouring disappears more and more the more perfect the mimicry 

 of the model becomes, until, finally, the model is repeated on the 

 under surface also. Compare, for instance, Figs. 30 and 32. From 

 this we may conclude that a dress which makes Lepidoptera appear 

 unpalatable morsels is a more effective protection than resemblance 

 to a leaf. That might indeed be deduced even from the theoiy, for 

 resemblance to a leaf never protects absolutely, and does so, in any 

 case, only during rest, while apparent unpalatability repels assailants 

 at all times. 



Those unversed in butterfly lore usually ask, when these mimetic 

 relations are expounded to them, how we know that copies which are 

 so like their models really belong to a different genus, or even family. 

 There are certainly cases in which model and copy resemble each 

 other so closely that even a zoologist cannot tell one from the other 

 without close examination, as, for instance, in the case of certain 

 transparent-winged Heliconiidge of Brazil (Ithomiides) and their 

 mimics belonging to the family of Whites. But even in such cases 

 the likeness only extends as far as is theoretically requisite, that is, 

 only to those characters that make the butterfly appear to the eye 

 of its pursuer like another species, known to it to be unpalatable. 

 The likeness does not extend to details, which can only be seen with 

 a magnifying-glass or a microscope, and above all, it does not extend 

 to the caterpillar, pupa, or egg. Thus, in the case cited, we may be 

 certain that the caterpillar of Ithomia is quite different from that 

 of the mimicking White, since the former will be, in structure, of the 

 type of Ithomia caterpillar, and the other of the usual type of 

 Whites. As yet, indeed, these two species are not known in their 

 caterpillar stages, but other cases are known. A species belonging 

 to the same genus as our indigenous 'kingfishers' (Limenitis populi), 

 a diurnal butterfly of North America, Limenitis arckippus (PI. I, 

 Fig. 9), strongly resembles the brown-yellow, immune Danais erippus 

 (PI. I, Fig. 8), while the caterpillars of both species are quite different, 

 that of Danais erippus possessing the remarkable, soft and flexible 

 horn-like processes of the Danaid caterpillars (PI. I, Fig. 10 a), while 

 the caterpillar of Limenitis arckippus (PI. I, Fig. n«) is at once 

 recognizable by its blunt, club-shaped and spinose papillae as a Limenitis 

 caterpillar. The adaptation of the butterfly to its protected model has 



