PEOTECTIYE MIMICRY. 233 



disappearance of all insects with warning colours during the 

 seasons when insect-life is scarce," and therefore in great 

 requisition by insect-eating birds. During the earlier and 

 later months of the year, anything in the shape of an insect 

 would be eagerly snapped up, and warning colours would 

 become a danger signal, not to the bird, but to the insect 

 itself. In spite, therefore, of the similarity in colour and 

 habit between the two moths mentioned above, it seems to me 

 that the position taken up by Mr. Poulton is too strong a one 

 to be overthrown. The onlj- alternative to supposing that 

 resemblance, however detailed and remarkable, to be a striking 

 coincidence, is to assume a recent change of time of emergence, 

 which has simultaneously affected both species ; but this is, if 

 possible, even more difficult of belief. 



Mimicry in some Cases possibly only a Resemblance due to Affinity. 



Another consideration must be kept in mind, in weighing 

 the arguments for and against the theory of Mimicry ; and 

 that is, how far the resemblances are due to affinity. Of 

 course, we may at once dismiss from this category such 

 examples as that afforded by Mimonectes. But with regard 

 to different families or genera of butterflies and moths, which 

 display mimetic resemblances, these considerations demand 

 investigation. It is a fact quite familiar to every zoologist 

 that, in certain members of a group, characters now and then 

 are noted, which betray its relationship , to another group. 

 These characters may have been inherited from the common 

 stock whence both groups were derived, or they may possibly 

 be in some cases a reversion to that stock. 



All existing birds, with the exception of one genus, Palamedea 

 (the Screamers), have bony outgrowths — the uncinate processes 

 — attached to their ribs, which serve for the more secure fixing 



