6 
SOUTH-AFRICAN BUTTERFLIES. 
The gregarious and onward-flying habits of the Pierince are well 
known, and reach their climax in the genus Callidryas (see infra, 
p. 185, and vol. i. p. 31), whose species have exceptional powers of 
flight, well indicated by their large, solid thorax and thick, strongly- 
veined wings. 
Mimicry is strikingly exhibited in this Sub-Family, and it was mainly 
the study of the deceptively exact imitation of various South- Ameri- 
can Danaince by species of the Pierine genus Leptalis that enabled Mr. 
Bates to give to science the satisfactory explanation of the phenome- 
non to which I have adverted in vol. i. pp. 35—36. The $ s of PerrlnjhriSj 
a genus very closely allied to Fieris, and a species of Euterpe, also 
mimic various Danaince; and one of the latter genus {E. Tereas) closely 
imitates the $ Papilio Zacyntlius. Mr. Wallace, in the paper above 
cited, commented on the imitation by the ^ s of various Malayan species 
of Eronia of the common kinds of Danais in the same region, and 
further brought to notice that mimicry occurred within the limits of 
the Pierince themselves, specifying several cases in which the slow-flying 
and showy species of Thyca are simulated by species of the genera 
Prioneris and Pieris. 
I am able to adduce two similar cases in South Africa, where the 
slow-flying Mylothris Agathina is nearly copied by both sexes of Pieris 
Thysa and by the female of Eronia Argia ; while in Western Africa 
Mylothris Poppea (Oram.) is the model followed by Pieris Rlwdope (Fab.). 
The genus which is by far the best developed in South Africa is 
Teracolus, white or yellow butterflies with a patch of bright colour — 
orange, red, crimson, or violet — at the tip of the fore-wings. I have 
discussed at length {infra, p. 82) the various groups of this large and 
most difficult genus, which contains some of the most beautiful of all 
the Pierince. 
Seasonal dimorphism — or palpable difference between the earlier 
and later broods of the same species — has been shown to occur in the 
well-known cases of Pieris Napi (Linn.), of which P. Bryonice (Ochs.) 
is the early or " winter" form, and Anthocharis Ausonia (Hiibn.), of 
which A. Belia (Cram.) is the " winter " brood. The progress of 
observation of the life-history of butterflies has of late years gone to 
show that instances of this kind of dimorphism are not, as was sup- 
posed, limited to countries where a severe winter prevails, but occur 
(and are probably more numerous) in tropical and sub-tropical regions 
where the climate is divided into wet and dry seasons.-^ Three cases 
in South Africa certainly exist, viz., those of Pieris CJiarina, Boisd., 
P. Thysa, Hopff., and P. Severina (Cram.), in each of which the winter 
or dry-season brood on the South-East coast is considerably smaller, 
and in the two latter with enlarged black markings. Probable cases 
are that Pieris alha (Wallengr.) is the dry-season brood of P. Pigea, 
^ See Mr. L. de Nice villa's paper on Calcutta Satyr ivce in the Journal of the Asiatic 
Society of BevgaJ, vol. Iv. p. 239 (1886). 
