264 THE COLOURS OF ANIMALS 



Tau) has an eye-like mark which it can expose when 

 attacked, but which is otherwise concealed. The 

 appearance of the larva in its terrifying attitude is 

 shown in fig. 58. 



Fig. 58.— The larva of Aglia Tau in its terrifying attitude -vsatji the eye-like 

 mark exposed ; full-fed ; natural size. 



It is obvious that this kind of intimidation re- 

 quires a caterpillar of a considerable size in order to 

 carry it off ; and as a matter of fact we never find it 

 attempted by small caterpillars. A full-grown Large 

 Elephant Hawk is quite as thick as a small snake, and 

 when partly hidden among leaves its length might be 

 safely left to the imagination. 



Some reasons why Mimicry is so frequent and perfect in 

 Insects 



Although mimetic resemblances are far commoner 

 and more perfect among insects than any other group 

 of animals, the phenomena will probably be found to 

 occur very widely when attention is directed to the 

 subject. It is, however, very unlikely that any one 

 group of animals employs this method of defence to 

 an extent which at all approaches the insects. The 

 defenceless character of the group as a whole, the 



