226 THE COLOURATION OF INSECTS 



abundant, shy, and easily alarmed, and there was no 

 evidence that they also were distasteful. On reflection 

 it is quite obvious that a mimic must be less abundant 

 than its model, for if, of a series of conspicuous insects 

 met with some are edible and others distasteful, an enemy 

 might find it worth while to catch every one he saw on 

 the chance of it being edible. If, however, the proportion 

 of edible to distasteful is very low, the chance of finding 

 an edible specimen is too small to make it worth while 

 catching large numbers that will not be eaten. 



The mimic, as has been said, is easily alarmed, and it 

 is not difficult to understand the reason. It has been 

 pointed out above that aposematic species, which serve 

 as models, are extremely resistant to harm, and even 

 if caught and tasted do not of necessity suffer vital 

 injury. Mimics, however, come from a stock which has 

 in the past relied for safety upon concealment or rapidity 

 of flight, and have not developed the toughness of their 

 models ; hence a nip by a bird's beak or the rough handling 

 of a monkey may cause fatal damage. 



So that one finds by experience that so long as mimics 

 are not alarmed, they have a great resemblance in move- 

 ment and habits to the aposematic species with which they 

 are associated. If a mimic is frightened it takes to flight 

 and dashes off at a great speed, whereas the model 

 will merely move a little way, and often come back 

 to the same spot, or may not even deign to move away 

 at all. 



Here again is well exemplified the action of natural 

 selection in producing changes, not only in colouration 

 and shape, but in the nervous system also, yet only so 

 far as such changes are required. Thus in certain mimetic 

 South American Pierines, a small part of the fore wing 

 that is normally concealed by the hind wing retains the 

 hue from which this grouji has derived the name of 

 " Whites," while the visible areas of the wings are mimetic 



