68 BUTTERFLIES 



not be eaten, or at any rate killed, by mistake. 

 Their object, therefore, is not to escape notice, but 

 to be readily seen and recognised. The best 

 examples of these are found in three great 

 families of butterflies the Heliconidae, found in 

 South America, the Danaidae, found in Asia and 

 tropical regions generally, and the Acraeidae of 

 Africa. These have large but rather weak wings 

 and fly slowly. They are always very abundant, 

 and all have conspicuous colours or markings and 

 often a peculiar form of flight ; characters by 

 which they can be recognised at a glance. The 

 colours are nearly always the same on both upper 

 and under surfaces of the wings, and they never try 

 to conceal themselves, but rest on the upper 

 surfaces of leaves and flowers. Moreover, they all 

 have juices which exhale a powerful scent ; so that 

 if they are killed by pinching the body a liquid 

 exudes which stains the fingers yellow, and leaves 

 an odour which can only be removed by repeated 

 washing. This odour is not very offensive to man, 

 but has been shown by experiment to be so to 

 birds and other insect-eating animals. 



Another example is furnished by the skunk, 

 which, although not included in the immediate 

 subject of this lecture, may be mentioned as an 

 extreme case illustrating the point we are con- 

 sidering. Concerning this animal I cannot do 

 better than quote Mr. Wallace again: "This 

 animal possesses, as is well known, a most offensive 

 secretion which it has the power of ejecting over 

 its enemies, and which effectually protects it from 



