COLOURS OF ANIMALS 



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various families. As a general rule the species were 

 smaller and much less brilliant in colours than those of 

 Mexico and South Brazil. The species too, although 

 numerous, were not represented by great numbers of 

 individuals ; they were also extremely nimble, and 

 therefore much less easy of capture than insects of the 

 same order in temperate climates. On the sandy beach 

 I found two species of Tetracha, a genus of tiger-beetles, 

 which have remarkably large heads, and are found only 

 in hot climates. They come forth at night, in the day- 

 time remaining hid in their burrows several inches deep 

 in the light soil. Their powers of running exceed every- 

 thing I witnessed in this style of insect locomotion. They 

 run in a serpentine course over the smooth sand, and 

 when closely pursued by the fingers in the endeavour 

 to seize them, are apt to turn suddenly back, and thus 

 baffle the most practised hand and eye. I afterwards be- 

 came much interested in these insects on several accounts, 

 one of which was that they afforded an illustration of a 

 curious problem in natural history. One of the Caripi 

 species (T. nocturna of Dejean) was of a pallid hue like 

 the sand over which it ran ; the other was a brilliant 

 copper-coloured kind (T. pallipes of Klug). Many insects 

 whose abode is the sandy beaches are white in colour ; 

 I found a large earwig and a mole-cricket of this hue 

 very common in these localities. Now it has been often 

 said, when insects, lizards, snakes, and other animals, 

 are coloured so as to resemble the objects on which they 

 live, that such is a provision of nature, the assimilation 

 of colours being given 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 assimilation 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 Tetra- 

 chas is coloured to resemble the sand, whilst its sister 

 species is a conspicuous 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 aie 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 



