16 COSMIC FRILOSOfEY, [ft. u, 



and ground-beetles emit a disagreeable, pungent smell, and 



they are often conspicuously coloured. But the most 



wonderful of all are the cases of protective mimicry. The 



heliconidse are among the most beautiful of South American 



butterflies. Being never eaten by birds, on account of a 



nauseous liquid which exudes from them when touched, they 



are not only very lazy Hyers, but have the under sides of their 



wings as gorgeously tinted as the upper side, so that they 



can be seen from quite a long distance. From the same 



cause they are prodigiously numerous, swarming in all the 



tropical forests. Now it is obvious that if another butterfly, 



not protected by a disagreeable odour or taste, were to 



resemble the heliconia in colouring, it would be as efiiciently 



protected as by imitating a dead leaf or dry twig; provided 



that there were but few of these butterflies among a large 



number of heliconias. For, as Mr. Wallace says, "if the 



birds could not distinguish the two kinds externally, and there 



were on the average only one eatable among fifty uneatable, 



they would soon give up seeking for the eatable ones, even if 



they knew them to exist." Now along with the heliconidse 



there does, in fact, live a distinct family of butterflies, the 



pieridse, most of which are white, and which are anatomically 



as distinct from the heliconidpe as a lion from a buffalo. 



But of these pieridse there is one genus, the leptalis, which 



exactly resembles the heliconias in external appearance. So 



close is the resemblance that such expert naturalists as Mr. 



Bates and Mr, Wallace have been repeatedly deceived by it 



at the time of capture. Moreover, each species of this genus 



leptalis is a copy of the ;)articular species of heliconia 



which lives in the same district. Every band and sjDOt and 



fleck of colour in the heliconia is accurately reproduced in 



the leptalis ; and besides this, the lazy mode of fliglit is also 



imitated. While in point of numbers, we find about one 



leptalis to a thousand heliconias. Nor is this the only 



instance. So pie-eminently favoured are these beautiful 



