PDF - Wallace Online

56 NATURAL SELECTIONfinremarkable. They are so abundant and characteristic inall the woody portions of the American tropics, that inalmost every locality they will be seen more frequently thanany other butterflies. They are distinguished by very elongatewings, body, and antennae, and are exceedingly beautifuland varied in their colours ; spots and patches of yellow, red,or pure white upon a black, blue, or brown ground beingmost general. They frequent the forests chiefly, and all flyslowly and weakly ; yet although they are so conspicuous,and could certainly be caught by insectivorous birds moreeasily than almost any other insects, their great abundanceall over the wide region they inhabit shows that they are notso persecuted. It is to be especially remarked also, that theypossess no adaptive colouring to protect them during repose,for the under side of their wings presents the same, or at leastan equally conspicuous colouring as the upper side and; theymay be observed after sunset suspended at the end of twigsand leaves, where they have taken up their station for thenight, fully exposed to the attacks of enemies if they haveany. These beautiful insects possess, however, a strongpungent semi-aromatic or medicinal odour, which seems topervade all the juices of their system. When the entomologistsqueezes the breast of one of them between his fingers tokill it, a yellow liquid exudes which stains the skin, and thesmell of which can only be got rid of by time and repeatedwashings. Here we have probably the cause of their immunityfrom attack, since there is a great deal of evidence toshow that certain insects are so disgusting to birds that theywill under no circumstances touch them. Mr. Stainton hasobserved 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 mothwhich happened to be among them. Young pheasants andpartridges which eat many kinds of caterpillars seem to havean absolute dread of that of the common currant moth, whichthey will never touch, and tomtits as well as other small birdsappear never to eat the same species. In the case of theHeliconidae, however, we have some direct evidence to thesame effect. In the Brazilian forests there are great numbersof insectivorous birds as jacamars, trogons, and puffbirds