5 8 MIMICRY AND HOMOPLASY 



There are very many examples, chiefly amongst 

 insects and other arthropods, at all stages of 

 growth and metamorphosis, of resemblances to 

 fragments of vegetation, excrescences on bark, 

 droppings, etc. It is usually not difficult to dis- 

 criminate between effective resemblances which 

 are objective, and fanciful resemblances which 

 are subjective. With the latter I have nothing 

 to do here, although they are sometimes of such 

 a nature as to have given rise to enduring popular 

 traditions, and on that account are entitled to 

 respect within their own scope. 



The resemblance to a common fundamental 

 form is well illustrated by the leaf-mimics, of 

 which the best known are the Leaf Butterflies 

 and the Leaf Insects. Mr Wallace remarks 

 that " many butterflies, in all parts of the world, 

 resemble dead leaves on their under side, but 

 those in which this form of protection is carried 

 to the greatest perfection are the species of the 

 Eastern genus Kallima" This genus of butter- 

 flies is noted for the extreme amount of indi- 

 vidual variation in the markings on the under 

 side of the wings, simulating all degrees of decay 

 and discoloration and fungus-attack ; to this must 

 be added the perfect leaf-shape and veining of 

 the closed wings. Besides all this, its method 

 of alighting is such as to complete the illusion. 

 Referring in particular to the Sumatran species 

 Wallace says that "this is effected by the butter- 



