56 NATURAL SELECTION f in 



remarkable. They are so abundant and characteristic in 

 all the woody portions of the American tropics, that in 

 almost every locality they will be seen more frequently than 

 any other butterflies. They are distinguished by very elon- 

 gate wings, body, and antennae, and are exceedingly beautiful 

 and varied in their colours ; spots and patches of yellow, red, 

 or pure white upon a black, blue, or brown ground being 

 most general. They frequent the forests chiefly, and all fly 

 slowly and weakly ; yet although they are so conspicuous, 

 and could certainly be caught by insectivorous birds more 

 easily than almost any other insects, their great abundance 

 all over the wide region they inhabit shows that they are not 

 so persecuted. It is to be especially remarked also, that they 

 possess no adaptive colouring to protect them during repose, 

 for the under side of their wings presents the same, or at least 

 an equally conspicuous colouring as the upper side ; and they 

 may be observed after sunset suspended at the end of twigs 

 and leaves, where they have taken up their station for the 

 night, fully exposed to the attacks of enemies if they have 

 any. These beautiful insects possess, however, a strong 

 pungent semi-aromatic or medicinal odour, which seems to 

 pervade all the juices of their system. When the entomolo- 

 gist squeezes the breast of one of them between his fingers to 

 kill it, a yellow liquid exudes which stains the skin, and the 

 smell of which can only be got rid of by time and repeated 

 washings. Here we have probably the cause of their im- 

 munity from attack, since there is a great deal of evidence to 

 show that certain insects are so disgusting to birds that they 

 will under no circumstances touch them. Mr. Stainton has 

 observed that a brood of young turkeys greedily devoured all 

 the worthless moths he had amassed in a night's " sugaring," 

 yet one after another seized and rejected a single white moth 

 which happened to be among them. Young pheasants and 

 partridges which eat many kinds of caterpillars seem to have 

 an absolute dread of that of the common currant moth, which 

 they will never touch, and tomtits as well as other small birds 

 appear never to eat the same species. In the case of the 

 Heliconidae, however, we have some direct evidence to the 

 same effect. In the Brazilian forests there are great numbers 

 of insectivorous birds as jacamars, trogons, and puffbirds 



