Notes on Seasonal Dimorphism. 
419 
to the capture of these species in the Cape Colony, but 
local conditions and difference of climate may give very 
different results in districts widely separated. Thus in 
Natal, for instance, certain species of butterflies are on 
the wing along the coast belt long before the appearance 
of their congeners in the upper districts. 
Instances also occur of certain butterflies being double - 
brooded in one locality, whereas in another (with pre- 
sumably less favourable conditions of existence), the 
same species only appears once a year. 
According to the rules which I have adopted, the smaller 
size and ferruginous tinting of the underside of Fieris 
gallenga (H. G. Smith), would point to its being a 
winter form of Fieris spilleri. 1 caught P. gallenga 
plentifully in the Umvelosi Yalley, Zululand, during July 
and August, 1889, but on the Natal coast P. spilleri 
itself is a late autumn and early winter butterfly, as these 
dates of capture for the year 1 890 will show : — 
April 9th, one and two ?s. June 1st, one c?, and 
June 8th, one ^ . 
These dates point, as I have already said, to its being 
an autumn or early winter butterfly ; but, on the other 
hand, last season, in the last week of February, I caught 
one of the large light variety 9 of P. spilleri at the Kark- 
loof, and Mr. Hutchinson, at the same time and place, 
two more ? s of this variety. Strange to say, I do 
not remember observing any of the typical P. spilleri $ 
or ? on the wing at the same time. 
It is quite possible that in the warm valleys of the 
Umvelosi there may be a regular summer and autumn 
brood of P. spilleri, and that P. gallenga succeeds it in 
the late winter. It is also probable that the two forms of 
P. spilleri and P. gallenga succeed one another similarly 
in Natal ; but it is a rare fly in this part of the world, and 
has not, therefore, been much observed, except at the 
season when it is most in evidence. 
Fieris gidica to Fieris ahyssinica affords me one of the 
best illustrations of seasonal differentiation, for if circum- 
stantial evidence be worth anything, one should have no 
doubts as to the relationship of the two butterflies. Both 
P. gidica and P. ahyssinica are common butterflies along 
the Natal coast, and I have given them much attention. 
