VARIABLE PROTECTIVE RESEMBLANCE IN INSECTS 151 



is much stronger than that of the Hght varieties to 

 the leaves (see figs. 38 and 39). Two species, how- 

 ever, are ah-eady known in which the green stems and 



Fig 38. The larva of a continental Noctua (Calocala elocata) with the colour 

 adjusted to that of the dark twigs mixed with its food-plant ; nearly full-fed ; 



two-thirds natural size. 



Fig. 39.— The colour of a larva of the same species when only preen twigs and leaves 

 were supplied to it. The food-plant in both cases was black poplar (Populus 

 nigra) 



leaves cause the production of green larvae, so that the 

 concealment is very perfect. And we may be quite 

 sure that there are many other species with equal 

 powers. 



Experiments upon the larvae of the Brimstone Moth 



Lord Walsingham first pointed out to me that the 

 larvae of the Brimstone Moth (Rtimia cratcegata) vary 

 from brown to green, and through all intermediate 

 shades. I found that when brown objects were 



