42 The Irisli Naluralist. May, 



lioles, where the female is hidden from view 

 during incubation, and so does not need a 

 conceahng colour. 



Now 1 think this theory is a very clear and easily 

 understood one — whether we accept it or not — and 1 would 

 ask particular attention to that part of it (a most necessary 

 and cardinal part) which accounts for so many cases of 

 bright-plumaged females by the fact that they make their 

 nests in holes ; for I wish to put forward a totahy different 

 explanation from the one I have just been quoting for the 

 fact that birds which nest in holes have generally both 

 sexes brightly coloured. 



Let us turn for a moment from the subject of birds to 

 that of other bright-coloured animals. Dr. A. R. Wallace — 

 who was, 1 believe, the first author to connect the bright 

 colours of many hen-birds with the fact that they make 

 their nests in holes — was undoubtedly the first to explain 

 the bright tints of many other creatures as " warning-oli " 

 advertisements, saving the creature that wore them from 

 molestation by announcing beforehand to all enemies who 

 could read the signal that " this bright-coloured caterpillar 

 has a horribly nasty taste," " this brilliant wasp has a 

 sharp sting," this gorgeous butterfl}- \\ill lead you a long 

 chase, and probably give you nothing better for your pains 

 in the long run than a bit of its brittle wing-membrane, 

 with a coating of disagreeable dust-like scales." It seems 

 to me rather remarkable chat this principle of " Warning 

 Coloration " was never applied by Wallace to the subject 

 of Sex Colours — especially as he did not accept Darwin's 

 view that these colours were developed by female preference, 

 but j)ut forward instead a not very clear suggestion that 

 they were somehow a product of the male bird's energeti(" 

 temperament. It would surely have been a very jiatural 

 extension of his own well-known })rincij)le of \\'arning colour 

 to say that the bright ])lumage of a cock Chaffinch in new 

 spring dress is a warning to other cock-Chaffinches around 

 him that " here is a full-grown, healthy, strong militant 

 bird who is determined to hold his ground against rivals, 

 and if you choose to enter his territory you have a tough 



