ANIMAL SENSE PERCEPTIONS. 175 



deterrent quality, and that its bright colours are due to at present 

 unknown causes, and serve unknown purposes. 



Some brightly coloured animals have no warning colour or 

 other protection, but trust to their own intelligence to avoid 

 danger. Thus " the bright colour of the male Golden Oriole 

 renders it peculiarly liable to be attacked by the Sparrowhawk, 

 and in such a contingency the Oriole does not trust to his 

 Thrush-like flight enabling him to elude his tormentor in the 

 open, but on the earliest opportunity seeks refuge in the 

 densest thicket available as cover." * The Rose-coloured 

 Pastor, with the back, breast, and sides of an exquisite pale 

 pink, is observed in its continental haunts to frequent trees or 

 shrubs bearing rose-coloured flowers, such as the blossoms 

 of the pink azalea, among which the birds more easily escape 

 notice. t 



Many plants owe their protection from the ravages of grazing 

 animals to offensive odours, which to ourselves are unappre- 

 ciable while the leaves are intact, and these apparently possess 

 no warning colours, or, at all events, none of those glaring 

 hues on which the theory is founded. These, however, are 

 avoided by the animals from whom protection is required, 

 and who have either learned to distinguish the plants by their 

 appearance, or have a greater delicacy of smell than ourselves. 

 Grazing animals also avoid plants furnished with stinging hairs, 

 which certainly seems due to observation, and probably inherited 

 experience. The European nettles (Urtica dioica and U. urens) 

 are generally left alone, and how much more so the U. stimulans 

 of Java, the U. crenulata of India, and U. mentissima of Timor, 

 whose stinging hairs are capable of producing severe attacks of 

 tetanus as by snake-bites. J These plants, however, seem to 

 have developed no prominent warning colours as understood by 

 the theory ; while their protection is undoubtedly real and 

 efficient. The theory of warning colours is a brilliant sug- 

 gestion, but one which seems to demand of nature an unnecessary 

 effort to supplement protective qualities already sufficient. The 

 argument has been thoroughly advanced by Prof. Poulton, who 



* H. A. Macpherson, 'Roy. Nat. Hist.' vol. iii. p. 355. 



f Jno. Watson, ' Poachers and Poaching.' p. 319. 



I Cf. Kerner and Oliver, ' The Nat. Hist. Plants,' vol. i. p. 442. 



