Seasonal Dimorphism in African Butterflies. 109 



A. lygus exist (which is not directly stated by Mr. 

 Trimen) may link A. stenobea to typical A. lygus, and so 

 to A. csecilia, but that they are a seasonal form of it in 

 the extreme south seems exceedingly improbable ; they 

 are far more likely to be a mere albinistic sport, such as 

 occurs in many other species of Acrsea. This seems the 

 more probable from the fact that, as far as I have seen, 

 they are always females. 



It is not at all a conclusive argument that, because in 

 southern South Africa A. stenobea has not been found 

 associated with A. caldarena and because, in Mashunaland, 

 the latter occurs the whole year round without A. stenobea 

 making its appearance, the two do not occur as seasonal 

 forms of one species 'in any part of Africa. Nevertheless, 

 as all the forms of A. csecilia appear to occur chiefly in 

 Southern and South- Western Africa (although typical A. 

 csecilia is also found in Abyssinia), I think the claim of 

 A. caldarena to be regarded as distinct has a firm basis. 

 Regarding this species as a wet-season form, we then still 

 have to look for its dry development; and this leads me 

 to point out to Mr. Marshall that, when he assumes that 

 each species varies seasonally in the same way through- 

 out its entire range, or, because it does not vary in one 

 district, it therefore varies nowhere, he makes an assump- 

 tion which can be easily disproved by anybody in charge of 

 a sufficiently large and carefully collected series of 

 specimens.* 



When we see that A. zetes is the extreme wet develop, 

 ment in Sierra Leone of that brightly coloured type of 

 A. menippe found at Uganda, and that A. pseudegina is 

 the extreme wet development in Sierra Leone of the 

 southern A. natalica; whilst in both cases intermediate 

 forms occur, sometimes side by side with the wet form, 

 and sometimes, to the exclusion of both extremes, in inter- 

 mediate localities, we must be very careful not to be too 

 dogmatic in our statements respecting the constancy of 

 either the species themselves, or their seasonal varieties. 



(5). A. pudorina, Staud. = A. ch&eribula, Oberth. 



Accepting Mr. Marshall's correction as to the black- 

 tipped forms being " wet " and the forms without 

 black tips " dry/' it is curious that in this species 



* By which I mean a series labelled, not only with exact 

 localities, but with the dates of capture, and altitudes. 



