PROTECTIVE RESEMBLANCES— DIMORPHISM, ETC. 57 



harmonise with those that are most characteristic in 

 the corresponding seasons. 



The Buff- tip Moth {Pygcera hucephala) is very 

 perfectly concealed by resemblmg a broken piece of 

 decayed and lichen-covered stick. The cylindrical 

 shape is produced by the wings being rolled round the 

 body. A friend ^ has raised the objection that the 

 moth resembles a piece of stick cut cleanly at both 

 ends, an object which is never seen in nature. The 

 reply is that the purple and grey colour of the sides of 

 the moth, together with the pale yellow tint of the parts 

 which suggest the broken ends, present a most perfect 

 resemblance to wood in which decay has induced that 

 peculiar texture in which the tissue breaks shortly 

 and sharply, as if cut, on the application of slight 

 pressure or the force of an insignificant blow. 



The excreta of birds are also very commonly re- 

 sembled by moths as well as by caterpillars. This 

 is the case with the little Chinese Character (Cilix 

 spinula)y^ and with many grey and white Geometers 

 which rest on the upper sides of leaves with their 

 wings extended as if * set.' In this position they 

 forcibly suggest the appearance of birds' excrement 

 which has fallen on to a leaf from a great height, and 

 has therefore become flattened into a wide patch. In 

 spite of a faithful resemblance to such an object, these 

 moths possess very great beauty. 



» Dr. C. M. Chadwick, of Leeds. 



* Arthur Sidgwick, Journ. of the Rugby School Nat. Hist. Soc. 



