208 CAEIPf. Chap. Y. 



ofiven in order to conceal the creatures from the keen 

 eyes of insectivorous birds and other animals. This is 

 no doubt the right view, but some authors have found a 

 difficulty in the explanation on account of this assimila- 

 tion of colours being exhibited by some kinds and not by 

 others living in company with them ; the dress of some 

 species being in striking contrast to the colours of their 

 dwelling-place. One of our Tetrachas is coloured to 

 resemble the sand, whilst its sister species is a con- 

 spicuous object on the sand ; the white species, it may 

 be mentioned, being much more swift of foot than the 

 copper-coloured one. The margins of these sandy 

 beaches are frequented throughout the fine season by 

 flocks of sandpipers, who search for insects on moonlit 

 nights as well as by day. If one species of insect 

 obtains immunity from their onslaughts by its deceptive 

 resemblance to the sandy surface on which it runs, 

 why is not its sister species endowed in the same 

 way ? The answer is, that the dark-coloured kind 

 has means of protection of quite a different nature, 

 and therefore does not need the peculiar mode of dis- 

 guise enjoyed by its companion. When handled it emits 

 a strong, offensive, putrid and musky odour, a property 

 which the pale kind does not exhibit. Thus we see 

 that the fact of some species not exhibiting the same 

 adaptation of colours to dwelling-places as their com- 

 panion species does not throw doubt on the explana- 

 tion given of the adaptation, but is rather confirmatory 

 of it. 



The carnivorous beetles at Caripi were, like those of 

 Para, chiefly arboreal. Some were found under the bark 



