Chap. XL] BUTTERFLIES AND MOTHS. 403 



passed by at the distance of many yards, and no doubt of 

 every passing bird. 



I then applied to Mr. Wallace, who has an innate 

 genius for solving difficulties. After some consideration 

 he replied : " Most caterpillars require protection, as may 

 be inferred from some kinds being furnished with spines 

 or irritating hairs, and from many being colored green like 

 the leaves on which they feed, or curiously like the twigs 

 of the ti-ees on which they live." I may add as another 

 instance of protection, that there is a caterpillar of a moth, 

 as I am informed by Mr. J. Mansel Weale, which lives on 

 the mimosas in South Africa, and fabricates for itself a 

 case, quite undistinguishable from the surrounding thorns. 

 From such consideration Mr. Wallace thought it probable 

 that conspicuously-colored caterpillars were protected by 

 having a nauseous taste ; but as their skin is extremely 

 tender, 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 in- 

 sufficient to protect a cateri^illar unless some outward sign 

 indicated to its would-be destroyer that its prey was a dis- 

 gusting morsel." Under these circumstances it would 

 be highly advantageous to a caterpillar to be instanta- 

 neously 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. Jen- 

 ner Weir, who keeps a large number of birds in an aviary, 



'2 'Proc. Entomolog. Soc' Dec. 3, 1866, p. xlv., and March 4, 1867, 

 p. Ixxx. 



