TJie Colours of Animals. 107 



they frequent. It may, perhaps, be said that this 

 comparison fails, because the stripes of tigers are 

 perpendicular, while those of caterpillars are either 

 longitudinal or oblique. This, however, so far from 

 constituting a real difference, confirms the explana- 

 tion ; because in each case the direction of the lines 

 follows that of the foliage. The tiger, walking 

 horizontally on the ground, has transverse bars ; 

 the caterpillar, clinging to the grass in a vertical 

 position, has longitudinal lines; while those which 

 live on large-veined leaves have oblique lines, like 

 the oblique ribs of the leaves. 



5. It might, however, be suggested that the cases 

 given above are exceptional. I have, therefore, in 

 another work, tabulated all our larger British cater- 

 pillars, and the result is very interesting. As regards 

 butterflies, we have 66 species, out of which 1 8 are 

 spiny, and two may fairly be called hairy. I do 

 not speak of mere pubescence, but of true hairs and 

 spines. Now, out of these 20, 10 are black, two 

 greyish, six brown or brownish, one greyish-green, 

 and only one green. Thus, while green is so pre- 

 ponderating a colour among smooth-skinned or 

 ordinarily pubescent* caterpillars (37 out of the 

 66 species of butterflies being of this colour), only 

 a single spiny species is thus coloured. 



6. Now let us look at these numbers under a 

 different aspect. Out of 66 species 10 are black; 

 and, as we have already seen, all these are spiny or 



* " Pubescent" means covered with very short fine hairs. 



