IN DEFENSIVE COLORATION 299 



IS seen in the green pipe-fish {Siphonostoma typhle *) ^ con- 

 spicuous in the weedless water, but well concealed among 

 the leaves of Zostera, The brown Lappet moth 

 {Gastropacha q^cercifolia^) conspicuous on a smooth deal 

 board, but well concealed among dead leaves, serves to 

 show that colour and shape cannot be correctly inter- 

 preted except by reference to the natural environment. 

 Many examples of the Protective Resemblance to dead 

 leaves are given on pp. 203-6. Mr. Abbott H. Thayer 

 has pointed out ^ that many species bear upon the under 

 surface of the wings the representation of shadows as 

 they are cast by such thin objects as dead leaves lying 

 one over the other on the ground. 



I. The Neutralization of Shadow, — The colours of 

 large numbers of animals are darkest on the back, 

 becoming gradually lighter on the sides, and passing into 

 white on the belly. Abbott H . Thayer ^ has suggested 

 that this gradation obliterates the appearance of solidity, 

 which is due to shadow. A colour-harmony, which is 

 also essential to concealment, is produced because the 

 back is of the same tint as the environment (viz. earth), 

 bathed in the cold blue-white of the sky, while the belly, 

 being cold blue-white bathed in shadow and yellow 

 earth reflections, produces the same effect. Thayer has 

 made and presented models to the Natural History 

 Museums of Oxford, Cambridge, and London, which 

 support his interpretation in a very convincing manner. 



Special resemblances to twigs, upright stems, &c., are, 

 Mr. Thayer considers, represented upon a background in 

 which the shadow is neutralized as described above. 

 Hence the background, viz. the animal's body, disappears, 

 while the markings upon it are alone distinctly seen. 



For ages the artist has known how to produce the 

 appearance of solid objects standing out on his canvas, 

 by painting in the likeness of the shadows. It has 

 remained for this ereat artist-naturalist to realize the 



' The asterisk added to this and the following examples indicates that 

 they were employed as lecture illustrations at Leeds in 1890. 

 ^ Trans. Ejit. Soc, Lond., 1903, p. 557. 

 ^ The Auk, vol. xiii, 1896, pp. 124 and 318. 



