EURASIAN & AUSTRALIAN NEPTINI 119 



Phaedyma columella (Cramer) 



This species seems to be exceptionally susceptible in most parts of its range to 

 local as well as seasonal influences, forms ranging from extreme ' wet season form ', 

 with deep purple-brown under surface ground colour, to ' dry season form ', with 

 ochreous under surface ground colour and much wider white markings, apparently 

 occurring almost independently of season. For example, in early September, 

 1934, in North Bengal (Teesta Valley) I took a dry season form at a time of heat 

 and high humidity, accompanied by daily torrential downpours, when only extreme 

 wet season form should have been expected. In some areas a range of intermediates 

 seems to occur almost throughout the year. A further feature in which the male 

 shows unusual instability is the length of the hind wing discal band on the under 

 surface ; it usually ends at vein 6 but may extend almost to vein 8. In some sub- 

 species examples with an extended discal band occur more frequently than in 

 others, but the feature is an unreliable subspecific character. Both these variable 

 features make it difficult to delimit subspecies with any precision, and to this must 

 be added the tendency of species which favour secondary growth and cultivation, 

 of which Ph. columella is one, to spread rapidly wherever suitable conditions exist. 

 With the increasing man-made expansion of suitable areas for colonization, subspecific 

 boundaries are naturally blurred in continental areas. In island groups, such as 

 the Philippines, successful invasions from one island to another must become more 

 frequent and lead initially to mixed populations, such as appears to occur in Min- 

 danao (see below), and ultimately to near stability. The larger the island the greater 

 will be the number of such invasions, which will then meet few land barriers to 

 their further spread. In small islands, like Camiguin de Mindanao, the chances of a 

 stray butterfly making a successful landfall are reduced, and the very occasional 

 introduction of a foreign strain may be followed by its absorption and total sub- 

 mergence in the native strain before further reinforcement arrives from overseas. 

 This is probably the main reason why small islands, with evolution producing a 

 quicker effect amongst their smaller populations, are able to develop and maintain 

 local microsubspecies which differ markedly from the forms found in larger neigh- 

 bouring territories. Good examples of this phenomenon in the Neptini are furnished 

 in the S.E. Asian area by Camiguin de Mindanao, Tioman Is. and the islands of 

 Paramalaya and in the Papuan subregion by Dampier Is. 



Ph. columella columella (Cramer) 



Papilio columella Cramer, 1780 : 15, pi. 296, figs. A, B $. China. 



Acca columena Hiibner, 18 19 : 44. 



Phaedyma columella tonkiniana Fruhstorfer, 1905c : 90, pi. 6, fig. 3 $. <£$ Tonkin, syn. n. 



Types Paris. 

 Neptis (Phaedyma) columella columella (Cramer) Fruhstorfer, 1913 : 615. 

 Neptis (Phaedyma) columella tonkiniana (Fruhstorfer) Fruhstorfer, 1913 : 615. 



South China, Hong Kong, Hainan, Tonkin. 



