WAKNING COLOUES 195 



must be as conspicuous at rest as it is on the wing, 

 a fact which is characteristic of those groups of 

 butterflies which are specially defended by being un- 

 palatable. In North America Danais archippus is 

 mimicked by Limenitis misippus, a butterfly belonging 

 to a very different group. 



Although the general resemblance between the 

 species in each of these groups is doubtless due to 

 arrested divergence, there is one very interesting 

 case which is probably to be explained by convergence 

 of groups which were formerly unlike. The Danaids, 

 which are found in the same localities as the Heli- 

 conias of tropical America, have taken the peculiar 

 appearance of the latter, in the arrangement of the 

 colours, and in the long narrow form of the wings. 

 These Heliconoid Danaids are therefore distinguished 

 from all the other members of the group. It is quite 

 obvious that both Heliconian and Danaids are benefited 

 by the fact that the insect-eating animals of the region 

 they inhabit have to learn but a single mode of flight, 

 shape of wing, and general arrangement of colours. 



Although these resemblances, produced by conver- 

 gence or by arrested divergence, are transitional into 

 and often contain an element of true Mimicry, they 

 must be distinguished from the latter. In true 

 Mimicry, the mimicking species are without unplea- 

 sant attributes, and are sheltered under the reputation 

 of abundant and well-known forms in which such 

 attributes are strongly marked. In the resemblances 



