296 THE COLOURS OF ANIMALS 



ceeded much farther in the same direction. In the 

 most degenerate species the female is a mere bag of 

 eggs, without limbs or sense organs ; she does not 

 even leave the pupa-case, but thrusts out the end of 

 her body that fertilisation may take place. In the pupa- 

 case of the most degenerate forms, no distinct trace of 

 former organs can be made out, but in that of certain 

 closely allied species they can still be recognised, 

 although in a very rudimentary condition; in others 

 again, still more distinctly. In the extreme forms 

 the degeneration of the female has proceeded as far 

 as it is possible to go, and in all it must be excessively 

 ancient. The males of nearly all Psycldda are cha- 

 racterised by a uniform sombre colour of a brown or 

 grey tint ; all bright colours and all traces of pattern 

 are almost invariably absent. 



The successive degrees of degeneration and atten- 

 dant loss of colour by the males have been traced in 

 species all of which belong to the Bombyces; the 

 males are in all cases day-flying. The day-flying 

 Bombyces, in which the females retain full possession 

 of their faculties, are remarkable for the brightness 

 and beauty of their colours, and this is true of species 

 which are probably without any special protection by 

 a disagreeable taste or smell. 



The condition presented by the Psychidce was sug- 

 gested to me by my friend Mr. W. White. I could give 

 many details which seem to explain the cause of the 

 degeneration, but this is unnecessary for the present 



