Seasonal Dmiorjphism in certain African Butterflies, 
timeSj and is_, in each, case, regarded as the principal 
cliaracter for distinguishing two otherwise similar species. 
Comparing tlie under surfaces, one sees either no 
difference whatever, or only such, as has a purely 
individual value ; whilst, occasionally, individuals come 
to hand in which the apical black patch of the upper 
surface varies between the two e:itreme types, clearly 
proving it to be valueless as a specific character ; 
A. acrita indeed is only one of those intermediate grades 
itself, for the black apex is still more largely developed 
in A. chseribula. 
These differences in Acrsea I believe to be seasonal ; the 
examples with the black apical patch being the wet- 
season forms. Supposing this to be a correct explanation 
of this curious and certainly inconstant difference, the 
species will stand as follows 
Dry-season form. Wet-season form. 
1. Acrasa anacreon, Trimen. ^Acrsea homhay H. G. Smith. 
2. Acrsea guillemei, Oberth. Acrasa periplianes, Oberth. 
Acraea doubledayi, Gaer. Acrsea dircsea, Westw. 
4. Acra;a stenobsea, Wallgr. Acrsea caldarena, Hewits. 
5. Acrsea pudorina. Stand. . Acrsea chseribula, Oberth. 
Witb regard to the above associations, it must be 
borne in mind that a species which, in a variable climate, 
is dimorphic, ceases to be so in a uniform climate, and 
thus it does not follow, because a species does not vary in 
one part of Africa, that it therefore shows equal constancy 
in another part : indeed, we now know that some of the 
Southern species which appear to breed from generation 
to generatioQ true to type, break up into two widely 
different types in Central Africa. Then, again, in a 
climate neither unusually dry nor wet, an intermediate 
type may prevail, to the exclusion of the extremes. 
Hitherto we bave not received typical A. pudorina from 
Nyasa-land, but we bave a form so near to it, that no 
Lepidopterist would have the temerity to describe it as a 
distinct specie^ ; secondly, we have typical A. acrita ; and, 
lastly, A. chseribula,-[ from Zomba. 
Climatic modifications and seasonal forms result 
* I cannot distinguish A . induna as a species, from this, 
t I consider this the same as ^4. ambigua, Crimen. 
