208 THE COLOUES OF ANIMALS 



tails and adjacent parts to a head in Thecla has been 

 long known : it was first observed by Dr. Arnold in 

 the case of a foreign species {Thecla larbas), and was 

 confirmed by Dr. Forsstrona in other species. The 

 fact is quoted by Kirby and Spence under ' Means of 

 Defence of Insects,' but the interpretation offered, that 

 the insects ' perhaps thus perplex or alarm their 

 assailants,' hardly expresses the true significance of 

 the character.^ 



The same fact was independently discovered by 

 Mr. K. C. L. Perkins in 1888, and this keen naturalist 

 at once perceived the meaning of the character — to 

 divert the attention of an enemy towards a non-vital 

 part. The discovery is of especial interest because it 

 was made upon an English species {Thecla W-alhum), 

 and because Mr. Perkins tested his explanation by 

 finding that this part had been torn in a considerable 

 proportion of the butterflies. 



The observation renders it extremely probable 

 that the slender ' tails ' which occur in the same 

 position in many * Blues ' {Polyojiimatus), and the 

 bright colours and eye-like spots which are often 

 associated with them, have a similar meaning. The 

 * Blues,' when resting on a flower, have the same 

 habit of moving the hind wings, as I have often ob- 

 served in our common English species which are 

 without ' tails.' The movement is such as would 

 render the ' tails ' prominent and antenna-like if 



' Kirby and Spence, People's Edition, 1867, p. 423. 



