144 THE COLOURS OF ANIMALS 



firmed, and has been extended to other species. Thus 

 Eev. W. J. H. Newman showed that the cocoons of the 

 Small Eggar Moth (Eriog aster lanestris) are creamy 

 white when spun upon white paper (see fig. 33), dark 



Fig. 33.— The cocoon of Small Eggar Pia. 34.— The cocoon of Small Eggar 

 Moth {E. lanestris), spun upon white spun among green leaves, 



paper ; natural size. 



brown when constructed among leaves (see fig. 34).^ 

 These cocoons are so compact and smooth that they re- 

 semble birds' eggs : a fact which explains the name of 

 the moth. In constructing the cocoon the caterpillar 

 leaves a few holes, which are doubtless of importance 

 in permitting a free exchange of air. The fact that 

 light reflected from green leaves is here the stimulus 

 for the production of a dark colour is readity intelligible 

 when we remember that the moth does not emerge till 

 the following February at the earliest, while the in- 

 sect often remains in the pupal state for one or two 

 years longer. The leaves in contact with the cocoon 

 soon die and turn brown, and after this change the 

 dark colour is highly protective. It is also of especial 

 importance for the cocoon to be well concealed during 

 the winter months, when insect-eating animals are 



' Froc. Ent. Soc. Lond. 1887» pp. 1. li. 



