088 DR. J. C, MOTTRAM OK 



Avas prepared, in one corner of which a, square e^'e-spot was 

 placed, in another corner a square of the same size and containing 

 the same proportion* of black and white but distributed on either 

 side of the diagonal, in a third angle a similar square divided 

 down the middle, the fourth angle was left unoccupied. This 

 square was then examined against various backgrounds. Two 

 facts were recorded : first, the eye-spot blended at a much shorter 

 distance than the other two black and white squares, and secondly, 

 the eye-spot square more effectively blurred the angle of the 

 gi-ey square than did the other two patterns. It was, however, 

 difficult to decide how much difference there really was, because 

 at the distance at which the eye-spot was blended and producing 

 blending at the corner of the square, the othei- two patterns had 

 not blended. In order to show the differences in the blending 

 distance : under the conditions of the experiment, the blending 

 distances of these patterns (text-fig. '6, 14- iO) were as follows: 

 eye-spot 18| feet, diagonally divided square 321 feet, medially 

 divided square 35 feet. Eye-spots distributed over a surface ai'e 

 often used for producing a pattern ; in Lepidoptera they often 

 form marginal patterns, but more frequently form patterns some 

 distance from the edge, as is also the case in the Jaguar (see 

 text-fig. 3, 17). 



It appears that a given quantity of black and white, used as 

 circular eye-spots, forms a pattern which obscures the outline, if 

 not better, at any rate as well as other patterns. In ordei' to 

 be effective in this respect the eye-spot, after blending, should 

 not make a contrast in tone with its ground ; this was found to 

 be the case as regards the eye-spots on the under wings of a 

 number of butterflies examined : for' instance, when the ground- 

 work was light, the dark in the ey8-«pot was either small or not 

 deep in tone. 



Other possible uses for eye-spots have been put forward : they 

 have been thought to be attraction marks which induce the 

 attacking enemy to strike them rather than vulnerable parts ; 

 they have been looked upon as " dazzlers " to divert the enemy's 

 eye from the insect as a whole. If one examines the larger eye- 

 spots and those on the dorsal surface of the wings of many 

 butterflies, one finds that they do not, after blending, harmonise 

 with the rest of the wing ; thus it woukl appear that they pro- 

 bably have a difierent function from those found on the under 

 wings, which it has been thought are fojr concealment. 



Patterns have been considered as regards their powers of con- 

 cealing form, against plain backgrounds only. Against mottled 

 backgyoundSj which probably are more common in nature, these 

 powers of concealment are as effective, not because they may 

 copy or be paintings of anything in the background (they may 

 be)," but because after blending they will cause the animal to fade 

 into its surroundings. 



Beyond the blending distance of n pattern, the question as to 



