326 The Descent of Man. Pakt 11 



Mr. Wallace remarks, " distastefulness alone would be insufficient 

 " to, protect a caterpillar unless some outward sign indicated to 

 " its would-be destroj'er that its prey was a disgusting morsel." 

 Under these circumstances it would be highly advantageous to 

 a caterpillar to be instantaneously and certainly recognised as 

 unpalatable by all birds and other animals. Thus the moet 

 gaudy colours would be serviceable, and might have been 

 gained by variation and the sui'vival of the most easily-re- 

 cogr.ised individuals. 



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

 was brought before the Entomological fciociety ^ 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 colour, and all which imitate twigs, are greedily 

 devoured by his birds. The hairy and spinose kinds are 

 invariably rejected, as were four conspicuously-coloured species. 

 When the birds rejected a caterpillar, they plainly shewed, by 

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

 disgusted by the taste.** Three conspicuous kinds of cater- 

 pillars 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 view is 

 confirmed, namely, that certain caterpillars have been made 

 conspicuous for their own good, so as to bo easily recognised by 

 their enemies, on nearly the same principle that poisons are sold 

 in coloured bottles by druggists for the good of man. We 

 cannot, however, at present thus explain the elegant diversity 

 in the colours of many caterpillars ; but any species which had 

 at some former period acquired a dull, mottled, or striped appear- 

 ance, either in imitation of surrounding objects, or from the 

 direct action of climate, &c., almost certainly would not become 

 uniform in colour, when its tints were rendered intense and 

 bright ; for in order to make a caterpillar merely conspicuous, 

 there would be no selection in any definite direction. 



Summary and Concluding hemarks on Insects. — Looking back 



8» * Proc. Entomolog. Soc' Dec. analogous facts in the * Third An- 



3rd, 1866, p. xlv., and March 4th, nual Report on the Noxious Insects 



1867, p. Ixxx. of Missouri,' 1871, p. 148. Som« 



** See Mr. J. Jennei* "Weir's opposed cases are, however, given by 



paper on Insects and Insectivorous Dr. Wallace and M. H. d'Orville; 



Birds, in' Transact. Ent. Soc' 1869, see 'Zoological Record,' 1869, p 



D. 21 , also Mr. Butler's paper, 049. 

 hid, p. 27. Mr. Riley has given 



