PROTECTIVE MIMICRY 223 



is to warn an enemy, as effectually as possible, of 

 real danger or unpleasantness ; while the object of 

 the unprotected forms in the fifth class is to suggest 

 the presence of some unpleasant attribute which has 

 no existence in fact. 



The transition from Warning to Mimetic colours 

 which occurs in the fourth class is no objection to 

 this arrangement ; for we cannot escape transition in 

 any classification of the uses of colour in animals. 

 Some authorities have failed to make any distinction 

 between Mimicry and the other forms of Protective and 

 Aggressive Resemblance ; but such an arrangement 

 would confound together cases in which appearance is 

 used for concealment, and those in which it is made 

 use of in order to attract attention. 1 



1 S. B. J. Skertchly has recently (Ann. and Mag. Nat. Hist., Series 

 vi. vol. iii. pp. 477 et aeq.) urged (a) that 'protective resemblance 

 copies stationary objects, mimicry simulates moving ones.' He accord- 

 ingly maintains that the former is a defence against enemies which 

 attack butterflies at rest, the latter against those which attack them 

 on the wing. He further argues that the attacks of birds constitute 

 the only real danger to an insect on the wing ; (6) that certain ob- 

 servers (Skertchly, Pryer, Scudder) agree in considering these attacks 

 to be of very little importance ; and (c) that therefore Mimicry, to- 

 gether with the shyness of moving objects exhibited by all butterflies 

 on the wing, ' are habits acquired long since, which have survived the 

 necessity that gave them birth.' He maintains that this argument 

 is supported by (d) the ' law that the amount of apprehended danger 

 is measurable by the efforts taken to avoid it,' inasmuch as ex- 

 amples of Mimicry are far rarer than examples of Protective Resem- 

 blance. 



To this^e may reply: (a) the alleged contrast between Pro- 

 tective Resemblance and Mimicry is only a usual consequence of the 

 real difference between them (see pp. 222-23, also p. 71). Further- 



