TRUE MIMICRY 99 



it, but it always settled down for a short time on a leaf, and soon 

 returned to its repast, whereupon the enemy ' instantaneously rushed 

 upon it in a fury, until at last he was obliged to give in,' abandoning 

 the attempt to catch a creature so adept in retreat. 



Many butterflies assemble at midday on sandbanks in the middle 

 of the river, in order to drink, and there, too, the lizards are always 

 lurking about. Hahnel gives a pretty and undoubtedly accurate 

 description of the protective value of the long tail borne by many of 

 the sail-like Papilios at the end of the posterior wing ; they ' quite 

 obviously' afford protection against the lizards, 'which, after 

 snapping, often find themselves obliged to be content with the tail 

 alone, while the rest of the animal flies away practically uninjured.' 



Not only is the great persecution of the butterflies a fact, the 

 immunity of the known species, which are models for mimicry, is 

 also certain. For numerous species, at any rate, this has now been 

 established. First of all — as has already been said — this is true of 

 the Heliconiidee, in regard to which Wallace long ago showed that, 

 if the thorax be pressed, they exude a yellowish juice of unpleasant 

 smell. This is probably the blood of the insect, but that does not 

 hinder the repulsive odour of the living butterfly being perceptible 

 at a distance of 'several paces,' as Seitz observed in Heliconius 

 besei. 



Repeated experiments have been made, which have shown that 

 such butterflies are rejected not only by. the insectivorous birds of 

 the primitive forest, but also by tame turkeys, pheasants and part- 

 ridges, usually so greedy. Hahnel has recently repeated these ex- 

 periments in Brazil with hens, and he obtained the same result. 

 The hens, ' which otherwise devoured all butterflies eagerly,' re- 

 jected all Ithomidse, Heliconiidse, the white Papilios, as also some of 

 the gaily coloured Heliconiid-like mpths which fly by day, such 

 as Usthema bicolor and Pericopis lycorea. Obviously, the gay or 

 conspicuous colour of these Lepidoptera acts as a warning signal of 

 their unpalatability, and protects them from attempts on the part 

 of the birds to investigate their flavour. Hence we find that the 

 under surface of these insects is coloured like the upper. Even the 

 numbers of these species which fly about indicates that they must 

 be little decimated, and, in point of fact, we never find the wings of 

 Heliconiidse lying on the ground in the forests of South America, 

 while those of the Nymphalidse and other butterflies are by no means 

 uncommonly seen as the remains of birds' meals. 



There is just as little room for doubt, as in the case of the 

 Heliconiidse and their allies, that the Danaidse, Acrseidse, and the 



