420 
Mr. Cecil W. Barker's 
Mr. Trimen, in his " South African Butterflies/' is 
disposed to regard P. ahyssinica as a local variety of 
P. gidica, were it not for the rarity of the former. Rarity 
certainly does not apply to it, in this locality, for in the 
winter season it is nearly as plentiful as P. gidica is during 
the summer months. P. gidica is on the wing through- 
out the summer, and is succeeded with seasonal regularity 
by P. ahyssinica in the winter, intermediate forms being 
fairly numerous during the change of the seasons. These 
intermediate forms show all the fuscous markings of ihe 
underside of P. gidica, in more or less suffused brown 
instead of black, but having the light yellow ground- 
colour only slightly affected by a duller tint. The upper 
part of the discoidal cell, which remains as a conspicuous 
whitish streak in P. ahyssinica, is also unaffected in the 
intermediate forms, except that the black streak bounding 
the lower parts of the cell of P. gidica has changed also 
to brownish, and has become somewhat broadened and 
suffused. In the typical ahyssinica the whole ground- 
colour has changed to brown, leaving only a whitish streak 
(still more contracted than in the intermediate form by 
the widening of the brown line of lower side of discoidal 
cell) from base through discoidal cell. The nervules and 
other markings peculiar to P. gidica are all shown in a 
darker shade of brown to that of the ground. I have 
also witnessed several cases of copulation of P. gidica 
with P. ahyssinica, or with the intermediate forms. 
This, of course, only occurs about the change of the 
seasons, when, generally, old worn ? s of the one kind 
are taken possession of by the early hatched ^ s of the 
other. 
Pieris severina also modifies seasonally, and is other- 
wise variable. The winter form has the nervules of the 
underside hindwings strongly defined in black, and has 
a dull greyish ground-colour to same. The black borders 
of the upperside are narrower than in the summer form, 
and in some $ examples the white spots of the hind- 
marginal border of hindwings are hardly enclosed. The 
late spring and early summer form retain the black 
clouded nervules of the underside, but the ground-colour 
between is light yellow instead of grey. A third form, 
which I have generally noticed as occurring in mid- 
summer, has very broad borders to upperside, often in 
the ^ almost obliterating the hindmarginal spots of the 
