ARTICLES 255 



Habits of the insects as given in Lepidoptera Indica : Nos. (1-5), (11-13), and 

 (15) no notes are given ; Nos. (6) and (7) beds of streams and trunks of trees at 

 rest ; (8) wooded country, no other note ; (9) in forest and open ground, quite fear- 

 less ; (10) margins of rivers and streams ; (14) river beds ; (16) flies very high and 

 fast ; (17) bathes in the water of streams like a swallow. 



There is thus little doubt that blue is commonly used in 

 warning colouration, and from the point of view of colour vision 

 it is clear why this should be the case Violet and red were 

 almost certainly the first two colours to become visually per- 

 ceptible ; for this reason blue, and more especially violet-blue, 

 would be used for conspicuous purposes, especially as the 

 majority of animals may still have only trichromic vision. 



If warning colouration is for short-distance visibility (see 

 p. 78), then blue and especially violet-blue should be the colour 

 for use at high illumination, because under this condition the 

 maximum visual perception is at orange-yellow far away from 

 blue-violet, and also because blue has small power of penetra- 

 tion and thus becomes at short distance dulled by the opacity 

 of the atmosphere. It has been seen that for other reasons red 

 should be the colour chiefly used at low (not nocturnal) illumina- 

 tions for warning purposes : if these premises be good, then 

 forest insects should present often red, rarely blue ; and insects 

 living in the full sunlight often blue and seldom red. The same 

 should hold with birds whose low-illuminated breasts should be 

 coloured red, and high-illuminated backs more often blue. It 

 has already been shown that in the insects under considera- 

 tion, red is chiefly found in forest species (red is very much more 

 commonly found in the nocturnal Lepidoptera than is blue). It 

 remains to analyse the habits of the blue insects given in Tables 

 3 and 4. This information is given in footnotes to these tables, 

 where it can be seen that the vast majority fly in open sunny 

 situations and that there is a striking contrast between their 

 habits and those of the shade-loving red insects (see p. 78). 

 The fact that large blue areas are found in the Kallima butter- 

 flies (see table No. 3) requires explanation, because these insects 

 do not belong to a protected group : in this case the blue appears 

 to be used to produce what may be called the conjuring effect : 

 the conjuror relies to a large extent for the delusion of his 

 audience upon making them look for the wrong thing. This is 

 exactly what a bright blue Kallima does when chased by an 

 enemy : it suddenly settles with closed wings and thus instantly 



