520 
Dr. A. G. Butler on 
African Species. 
Summer form. Winter form. 
4. Teracolus vesta, Reiche. Teracolus argillaceuSy'Butl. 
5. Teracolus aurig ineus ,^nt[. Teracolus venustus, Butl. 
6. Teracolus chrysonome,K\ug. 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 forewings, 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. 666-7) : — "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 difi'erence, by the arrival 
of a collection from Fwambo, B. C. Africa, in which we 
received an intermediate example " half-way between 
typical A. acrita SLuS. A. pudorina'' (See P.Z.S., 1895, 
p. 261), which led me to adopt a difi*erent 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 
