520 Dr. A. G. Butler on 



AFRICAN SPECIES. 

 Summer form. Winter form. 



4. Teracolus vesta, Reiche. Teracolus aryillaceus, Butl. 



5. Teracolus aurigineus^utl. Teracolus venustus, Butl. 



6. Teracolus chrysonome, Klug. Teracolus helvolus, Butl. 



7. Teracolus gaudens, Butl. Teracolus arenicoleus, Eutl. 



Seasonal dimorphism in butterflies is certainly much 

 commoner than is generally supposed, and when 

 thoroughly understood, will tend to explain away the 

 difficulties arising from a study of intermediate grades 

 between apparently distinct types, which will then be 

 seen to be merely dry and wet-season forms of one and 

 the same species. 



As an example, I may mention that in the genus Acrsea 

 Dr. Staudinger, some years since, described a species 

 under the name of A, pudorina, and he observed 

 " Hewitson regards this specimen as a doubtful variety of 

 his Acrita } a beautiful example of which I also possess 

 from Zanzibar. But Acrita has four to five large black 

 spots on the forewings, and notably a broad black apex 

 to the same, wherefore Pudorina can never belong to it." 

 In 1894 Mr. Trimen figured a variety, observing that 

 " Both sexes show a good deal of variation as regards the 

 width of the apical fuscous border in the forewiugs, and 

 in the numbers (seven or eight) and relative sizes of the 

 rounded discal spots in the hindwings," etc., and in the 

 same year I mentioned (P.Z.S., pp. 566-7) : " There is 

 not the slightest question that this (A. pudorina) is a 

 local representative of A. acrita, from which it only 

 differs in the absence of the broad apical black patch on 

 the primaries; in well-marked examples all the spots (on 

 the absence of which Dr. Staudinger relies) are well 

 defined ; one specimen even shows an additional spot on 

 the subcostal area, nearer to apex/' 



In 1895, however, I was forced to modify my opinion 

 as regards the local value of the difference, by the arrival 

 of a collection from Fwambo, B. C. Africa, in which we 

 received an intermediate example " half-way between 

 typical A. acrita and A. pudorina " (See P.Z.S., 1895, 

 p. 261), which led me to adopt a different view respecting 

 the meaning of this apical patch. 



Among the species of the group to which A. acrita 

 belongs, the apical black patch occurs no less than five 



