76 THE COLOURS OF ANIMALS 



give an advantage to the possessor in the constant 

 struggle for food. 



Adventitious Protection 



Before proceeding to describe the power of Vari- 

 able Protective Resemblance possessed by many 

 animals, it is necessary to point out that effects 

 similar to those described above may be gained by 

 means which supplement the acquisition of any special 

 colour and form, or which may entirely replace these 

 methods of producing concealment. Many animals 

 cover themselves with objects which are prevalent in 

 their surroundings and are of no interest to their 

 enemies. Sometimes the meaning of this habit is 

 concealment alone, but in other cases objects of great 

 strength are selected and bound firmly together so 

 as to form a resistant armour. 



Many Lepidopterous larvae live in cases made of 

 the fragments of the substance upon which they live. 

 The cases of the larvae of Clothes Moths are only too 

 well known ; those of the Psychidw are made of leaf 

 or brown grass stems. The larva of the Essex 

 Emerald Moth {Geometra smaragdaria) covers itself 

 with a loose case made of fragments of leaves spun 

 together with silk. The cocoons of Lepidoptera are 

 frequently concealed by containing fragments of wood 

 or bark gnawed off the surface on which the cocoon is 

 constructed {Cemra, Cilixy Hemerophila, &c.). Birds' 



