Notes on Seasonal Dimorphism, 
423 
as ever. Mr. Mansel Weale's testimony of the occur- 
rence of T. topha at King William^s Town, throughout 
the summer (from January to May, 1876), and of this 
species being replaced the following summer (from end 
of 1876 to end of April, 1877) by T, auxo is, in the light 
of my experience in Natal, difficult to account for. It 
however appears that T. auxo is at its furthest limits 
westwards in Brit. Kafifraria, and that it only occasionally 
puts in an appearance, being almost exclusively replaced 
by the allied form T. topha. It has already been men- 
tioned in this paper that as regards Mycalesus safitm, the 
variety evenus (Hopfif.), which represents our winter form 
of this fly, alone is met with at the Knysna. The Knysna 
represents the furthest limits westwards of M. safitza = 
M. evenus J as Brit. Kaffraria represents the western limit 
of T. auxo = T. topha, and in each the winter forms of 
the respective species are alone prevalent. But T, auxo 
is reported to have occurred near King William^s Town 
in 1877 in abundance. 
It is difficult to account for this occasional appearance 
of the Natal summer form auxo in Brit. Kaffraria, 
but cases do occur frequently (presumably in seasons 
favourable to such reversion), of forms peculiar to certain 
localities, showing marked differentiation towards allied 
forms of other localities. Per exemplum, Papilio hrasidas, 
a common fly in Natal, shows, in some seasons, a marked 
disposition to approximate to its allied form Papilio 
leonidas, and on the 7th of December, 1894, I captured 
a ? P. leonidas J which in the size and greenish colouring 
of the spots, could not be separated from the most 
pronounced type of Tropical Africa. 
Papilio morania shows the same inclination, in certain 
seasons, towards its allied form P. corinneus. P. 
morania and P. hrasidas are the local semi-tropical 
modifications of P. corinneus and P. leonidas re- 
spectively, and under favourable conditions of seasons 
there is a constant inclination to reversion towards the 
facies of their Tropical representatives. Similar causes 
may have produced analogous results as regards the 
occasional reversion in Brit. Kaffraria of T. topha to the 
T. auxo form, of the more humid semi-tropical eastern 
districts. 
Mr. Mansel Weale bred the larvse and pupae of both 
T. auxo and T. topha, and found them identical in 
