66 ON PLANTS AND INSECTS. [LECT. 



bits of stick, the similarity being much increased by the 

 peculiar attitudes they assume. On the other hand, the 

 large brown caterpillars of certain Sphingidce are night 

 feeders, concealing themselves on the ground by day ; 

 and it is remarkable that while species, such as S. con- 

 volvuli, which feed on low plants, turn brown as they 

 increase in age and size ; others, like the Smerinthi, 

 which frequent trees, and cannot therefore descend to 

 the ground for concealment, remain green throughout 

 life. Omitting these, we find in the table, among the 

 larger species, seventeen which are brown, of which 

 twelve are hairy, and two have extensile caudal fila- 

 ments. The others, though not Geometridce, closely 

 resemble bits of stick, and place themselves in peculiar, 

 and stiff attitudes. 



And thus, summing up the caterpillars, both of butter- 

 flies and moths, out of the eighty-eight spiny and hairy 

 species tabulated, only one is green (L. sybilla), and 

 even this may not be protectively coloured, since it has 

 yellow warts and white lateral lines. On the other 

 hand, a very great majority of the black and brown 

 caterpillars, as well as those more or less marked with 

 blue and red, are either hairy or spiny, or have some 

 special protection. 



Here, then, I think, we see reasons, for many at 

 any rate, of the variations of color and markings in 

 caterpillars, which at first sight seem so fantastic and 

 inexplicable. I should, however, produce an impression 

 very different from that which I wish to convey, were I 

 to lead you to suppose that all these varieties have been 

 explained, or are understood. Far from it ; they still 



