196 Dr. F. A. Dixey on 



noted by Piopers * that the uon-ocellateJ form, though on 

 the whole belonging chiefly to the dry season, is also to be 

 met with daring the rains. It is true, as Piepers says, that 

 in Java, as in the Malayan Islands generally, the distinc- 

 tion between dry and wet season is not so sharp as on the 

 Indian mainland ; so that a certain amount of inter- 

 mingling of the two forms might perhaps have been 

 antecedently expected. It does not appear, however, that 

 all dimorphic species are affected by these or the like 

 conditions in the same way. De Niceville points out, in a 

 passage quoted by Trimen, that with this exception of 

 Melanitis leda there are no dry-season forms in North-east 

 Sumatra; and Doherty mentions analogous facts in refer- 

 ence to localities with a generally moist climate, like 

 Ceylon and Singapore, and also, mutatis mutandis, to dry 

 countries like Sind.f The prevalence of wet-season 

 forms in the equatorial forest region of West Africa is 

 another phenomenon of the same kind. Instances such 

 as these show that a generally damp country may be 

 characterized by a greater abundance of " wet-season " 

 forms, and vice versa. But these cases of the prevalence 

 of " dry " or " wet-season " forms respectively, according to 

 the general climatic conditions of a given locality, are, as 

 we have just seen, accompanied by others which seem to 

 prove that in certain districts, especially perha[)S dry ones, 

 the phases that are usually associated with the seasons 

 occur indiscriminately at all times of the year. 



Many such instances are recapitulated by Butler in his 

 late revisions of the genera Teracolus and Terias. Teracolus 

 eupom^K, King, for example, has a wet, an intermediate 

 and a dry phase. " The two latter undoubtedly fly 

 together, and in Aden it is tolerably certain that all the 

 phases emerge at the same time as mere variations." J 

 With regard to T. halimede, King, Butler observes, " T. 

 acaste represents the wet-season phase, T. halimede the 



* "Die Failiunevolution bci den Pieridcn," Tijdsclir. der Nedorl. 

 Dierk. Vereenig; (2) Deel V, 1898, pj). 179— 185," etc. The value of 

 the theoretiral considerations based by Piepers on the facts that he 

 has evidently observed with miicli care, a])pears to me to be greatly 

 diminished by his refusal to admit the influence of selective 

 adaptation, even as a provisional liypothesis. 



t Pro>. Ent. Soc. London, 1898, p. Ixviii. Comi)are Watson ; 

 Journ. P.ondiay Nat. Hist. Soc, 1894, vol. viii, p. 489, etc. 



X Ann. Mag. Nat. Hist., 1897, vol. ii, p. 497. 



