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SCIENCE PROGRESS 



requisitioned. Each colour has been further classified accord- 

 ing as to whether any single mass of it occupied a large area 

 (more than two-thirds of either wing) ; a moderate area (more 

 than one-third of either wing) ; or a small area (less than one- 

 third of either wing). Omitting those species which mimic or 

 which present sexual colour differences, the distribution of 

 colour shown in diagram No. i results. It can be seen that 

 brown is found more often than any other colour, followed in 

 order by black, white, yellow, orange, red, blue and violet, and 

 lastly, green. Blue and violet are not considered separately. 

 As green foliage so commonly forms a background in Nature, 

 it is remarkable that butterflies do not more often present a 



500 



• 400 



i soo 



! 200 



■ 00 



B 



R 



O Y W 



Diagram No. I. 



G., green; B. , blue; R., red; O. , orange; Y. , yellow; W., white; Bl., black; Br., brown. Black 

 areas represent large areas of colour. Ruled areas represent moderate areas of colour. White areas 

 represent small areas of colour. 



green colouration, seeing that their patterns and colouration 

 in the vast majority of cases render them inconspicuous. Had 

 the colours of lepidopterous larvae been investigated, a much 

 greater use of green would be found, as well as a dimorphism 

 which may explain the rarity of green butterflies. It is not 

 uncommon for some individuals to be coloured brown, whilst 

 others of the same species are green ; and this dimorphism 

 occurs not infrequently in other insect groups. In many cases 

 this is not associated with either environmental differences or 

 differences of habit. If, however, cognisance be taken of the 

 evolution of colour vision, a ready explanation of this irregu- 

 larity is available. Red and violet were the colours to become 



