102 THE VARIATION OF ANIMALS IN NATURE 



or egg-shaped with no shoulders. The pronotum and other 

 parts vary in the same way. There are about forty-six types 

 of variation (such as long- and short-legged ; long-, short- or 

 a-mucronate-forms, etc.), which are liable to turn up in the 

 races of any species. The colour also varies, but may be 

 directly correlated with climatic conditions. In most European 

 Carabus variation within the species consists of many local 

 races, each of which is pretty constant. In Coptolabrus each 

 race is very variable and not nearly so sharply defined. 



(e) Lepidoptera. — Doubtless some of the most remarkable 

 cases are complicated by the phenomena of mimicry, but many 

 non-mimetic species are quite sufficiently remarkable. In 

 the mimetic forms the discontinuity between the various types 

 tends to be more marked. Of mimetic butterflies Heliconius 

 melpomene (Eltringham, 1916) is one of the most remarkable. 

 Eltringham united ten reputed species and 60-70 named 

 colour-forms, all of which are structurally indistinguishable. 

 Some of the forms are geographically limited, but often several 

 are found in one restricted locality. 



Fryer (1928) has studied the variation in England of the 

 moth Acalla comariana Zeller (Plate II). At Wisbech there are 

 six main forms which differ sharply from one another in colour, 

 the fundamental pattern being the same. Genetical inves- 

 tigations suggest that there are probably three allelomorphs 

 for ground colour and a factor for the colour of the costal 

 blotch which is strongly linked with the ground colour. The 

 proportions of the various forms were of the same order in 

 1926 and 1927 at Wisbech, but in Lancashire the proportions 

 were quite different and an additional type was discovered. 

 Other species of the genus are even more polymorphic, but 

 have not been investigated genetically. Sheldon (1 930-1 931) 

 has shown that there are almost innumerable varieties, many 

 of them sharply distinct from one another, in Acalla (Peronea) 

 cristana. 



3. Polymorphism combined with constancy in particular areas. 



Probably most polymorphic species are really of this 

 character. We rarely have enough data to show that all the 

 various forms occur throughout the range. There is always 

 a tendency to form non-variable colonies or even larger 

 populations. 



