MIMICRY 211 



a mimicking butterfly can be, after a short experience, 

 readily distinguished even when on the wing from its 

 model, and that therefore it is only reasonable to 

 suppose that the butterfly's enemies can readily pene- 

 trate the thin disguise, and consequently are not de- 

 ceived by the deceptive resemblance ; in other words, 

 the resemblance, not being sufficiently perfect, is 

 valueless to the insect. 



An observation of my own may throw a little fresh 

 light on this question. On Mt. Penrisen in Sarawak, 

 two of the commonest butterflies were Caduga larissa 

 and Tirumala crowleyi, species belonging to the sub- 

 family Danainat. These butterflies are black with 

 streaks of green on both surfaces of all the wings. 

 Like all the other members of the sub-family, these 

 two species were conspicuous by their abundance and 

 by their slow flaunting flight, and habit of settling 

 in exposed situations, so that they were quite as con- 

 spicuous when at rest as when on the wing. The 

 Danaince are regarded as a sub-family of distasteful 

 insects advertising their distasteful properties by the 

 means noted above. Before very long I had secured 

 enough specimens of both these two butterflies to 

 satisfy me, and subsequently when out butterfly hunt- 

 ing I used to ignore them. One day I saw approach- 

 ing me a butterfly which I took to be Caduga larissa, 

 and it was not until the insect had passed me quite 

 closely that I realized from its quicker flight and from 

 a slightly different style of wing-marking that here was 

 no Danaine, but a mimic Elymnias lais. The critical 

 moment, however, was past, and the butterfly was out 

 of reach. I saw it settle in a little thicket of thorny 

 rattan, and cautiously approached, but no sign of it 



