322 THE DESCENT OF MAN. 



"kinds being furnished with spines or irritating hairs, and from 

 "many being colored green lil^e the leaves on which they feed, 

 "or being curiously like the twigs of the trees on which they 

 "live." Another Instance of protection, furnished me by Mr. J. 

 Mansel Weale, may be added, namely, that there is a caterpillar 

 of a moth which lives on the mimosas in South Africa, and 

 fabricates for itself a case quite indistinguishable from the sur- 

 rounding thorns. From such considerations Mr. Wallace thought 

 it probable that conspicuously-colored caterpillars were protected 

 by having a nauseous taste; but as their skin is extremely ten- 

 der, and as their intestines readily protrude from a wound, a 

 slight peck from the beak of a bird would be as fatal to them 

 as if they had been devoured. Hence, as Mr. Wallace remarks, 

 "distastefulness alone would be insufficient to protect a cater- 

 "pillar unless some outward sign indicated to its would-be de- 

 "stroyer that its prey was a disgusting morsel." Under these 

 circumstances it would be highly advantageous to a caterpillar 

 to be instantaneously and certainly recognized as unpalatable by 

 all birds and other animals. Thus the most gaudy colors would 

 be serviceable, and might have been gained by variation and the 

 survival of the most easily-recognized individuals. 



This hypothesis appears at first sight very bold, but when it 

 was brought before the Entomological Society'' it was supported 

 by various statements; and Mr. J. Jenner Weir, who keeps a 

 large number of birds in an aviary, informs me that he has 

 made many trials, and finds no exception to the rule, that all 

 caterpillars of nocturnal and retiring habits with smooth skins, 

 all of a green color, and all which imitate twigs, are greedily 

 devoured by his birds. The hairy and spinose kinds are invari- 

 ably rejected, as were four conspicuously-colored species. When 

 the birds rejected a caterpillar, they plainly showed, by shaking 

 their heads, and cleansing their beaks, that they were disgusted 

 by the taste." Three conspicuous kinds of caterpillars and moths 

 were also given to some lizards and frogs, by Mr. A. Butler, and 

 were rejected, though other kinds were eagerly eaten. Thus the 

 probability of Mr. Wallace's vievvf is confirmed, namely, that cer- 

 tain caterpillars have been made conspicuous for their own good, 

 so as to be easily recognized by their enemies, on nearly the 

 same principle that poisons are sold in colored bottles by drug- 

 s' 'Proc. Bntomolog-. Soc' Dec. 3rd, 1866, p. xlv., and March 4th, 1867, 

 p. Ixxx. 



=' See Mr. J. Jenner Weir's paper on Insects and Insectivorous Birds, 

 in 'Transact. Ent. Soc' 1S69, p. 21, also Mr. Butler's paper, ibid. p. 27. 

 Mr. Riley has given analogous facts in the 'Third Annual Report on 

 the Noxious Insects of Missouri,' 1871, p. 148. Some opposed cases are. 

 however, given by Dr. Wallace and M. H. d'Orville; see 'Zoological 

 Record,' 1869, p. 349. 



