254 



DR. J. C. MOTTRAM ON CONCEALMENT BY 



blending, coloured areas in juxtaposition have the appearance of 

 standing out, one from the other, and occupying different planes. 



These appearances may be explained in another manner. The 

 mind largely recognises objects by their outline, and to some 

 extent judges their distance by its sharpness. If in representing 

 objects on a flat surface, they be edged with white or black lines, 

 then the sharp outline thus given will make them appear nearer 

 the eye than their surroundings, and the flat surface appear to be 

 disrupted in a plane at right angles to the surface. 



Surface Disi^ujytioyi in Animal Pattern. — Concealment in the 

 animals consists chiefly in the hiding of outline, solidity, and 

 surface. Outline is largely concealed by "Disruptive Coloration," 

 solidity by "Counter Shading/*' 



" Disruptive Coloration " conceals outline in the following 

 manner: when an animal covered with a number of large 

 patches of different tone and colour comes to rest on a back- 

 ground which harmonises with any one of the components, then 

 its characteristic outline will be broken, as shown in text-fig. 1. 



Text-figure 1. 



A BCD 



Disruptive Coloration: A, a pattern of three components which largely interrupt 

 the margin. 13, the appearance when seen against a background harmo- 

 nising with the spotted component, C and 1) when seen against a striped 

 and a plane background. 



The disruption is in the same plane as the wings of the insect, 

 and is dependent upon a pattern breaking out over a large portion 

 of the margin. 



Disruption of surface consists in an arrangement of pattern 

 and coloration, which causes some portion of the surface to 

 appear close to the eye, and others far away. In this case the 

 disruption is in a plane at right angles to the plane of the object. 

 As has already been shown, this can be produced by the use of 

 Simultaneous Contrast and, thus brought about, may be termed 

 Surface Disruption by Contrast. "Outline Disruption" and 

 " Surface Disruption by Contrast " are often combined as shown 

 in text-fig. 2 A (compare text-fig. 1 ). Text-fig. 2 B illustrates 

 an insect showing only Surface Disruption. 



An examination of British Lepidoptera is now made in order 

 to estimate to what extent this method is employed for purposes 



