INSECTS. 369 



Mr. Bates informs me, as an instance of this, that the most 

 conspicuous caterpillar which he ever beheld (that of a 

 Sphinx) lived on the large green leaves of a tree on the 

 open llanos of South America; it was about four inches in 

 length, transversely banded with black and yellow, and 

 with its head, legs and tail of a bright red. Hence it 

 caught the eye of any one who passed by, even at the 

 distance of many yards, and no doubt that 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 being curiously like the twigs of the trees 

 on which they live." Another instance of protection, fur- 

 nished me by Mr. J. Mansel Weale, may be added, namely, 

 that there is a caterpillar of a moth which lives on the 

 mimosas in S. Africa, and fabricates for itself a case quite 

 indistinguishable from the surrounding 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 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. Wal- 

 lace remarks, " distastefulness alone would be insufficient 

 to protect a caterpillar unless some outward sign indicated 

 to its would-be destroyer 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 service- 

 able, 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 



* " Proc. Entomolog. Soc.," Dec. 3, 1866, p. 45, and March 4, 1867, 

 p. 80. 



