120 THE ENEMIES OF BUTTERFLIES [ch. 



which were very strongly illuminated with blue. 

 Results of a similar nature were also obtained from 

 pigeons, and from a kestrel which was fed with pieces 

 of meat lighted with different colours. 



On the whole these experiments of Hess convey a 

 strong suggestion that the colour perceptions of birds 

 may be quite different from our own, more especially 

 where blue is concerned. Great caution is needed in 

 discussing instances of mimicry in their relation to 

 the bird, for we have no right to assume that the bird 

 sees things as we do. On the other hand, it is a matter 

 of much interest to find that in general blue plays 

 relatively little part in cases of mimetic resemblance 

 among butterflies; some combination of a dark tint 

 with either red, white, brown, or yellow being far more 

 common. 



It will probably be admitted by most people that 

 the evidence, taken all together, is hardly sufficient 

 for ascribing to birds that part in the establishing of a 

 mimetic likeness which is required on the theory of 

 mimicry. That birds destroy butterflies in considerable 

 numbers is certainly true, but it is no less true that some 

 of the most destructive birds appear to exercise no 

 choice in the species of butterfly attacked. They simply 

 take what comes first and is easiest to catch. It is 

 probably for this reason that the Wood-swallow feeds 

 chiefly on Euploeines and Danaines (cf. p. 112). It 

 is probably for this reason also that such a large pro- 

 portion of the records of attacks on butterflies under 

 natural conditions refer to the Pierines; for owing to 



