PKOTECTIVE RESEMBLANCES— DIMORPHISM, ETC. 51 



each individual has two or more appearances, as it 

 were, at its command, and can develop that one which 

 is most suited to its own peculiar surroundings. 



A reason for the wonderful concealment of Lepidopterous 

 larvae 



In the remarkable abundance and variety of 

 methods by which concealment is effected in Lepi- 

 dopterous larvae, we probably see a result of their 

 peculiarly defenceless condition. A larva is a soft- 

 walled cylindrical tube which owes its firmness, and 

 indeed the maintenance of its shape, to the fact that 

 it contains fluid under pressure, which is exerted by 

 the sides of the body. This construction is extremely 

 dangerous, for a slight wound entails great loss of 

 blood, while a moderate injury must prove fatal. 

 Hence larvae are so coloured as to avoid detection or 

 to warn of some unpleasant attribute, the object in 

 both cases being the same — to leave the larva un- 

 touched, a touch being practically fatal (see also 

 pp. 175-76). 



The concealment of Pupae 



Protective Kesemblance, either Special or General, 

 is seen in nearly all exposed pupae, but most chrysalides 

 are buried in the earth or protected by cocoons. The 

 cocoons are often sufficient defence, because the silk is 

 very unpleasant in the mouth ; but such protection 



