Notes on Seasonal Dimorpldsm. 557 



Frecis, I was not/ long in noticing that many of the spe- 

 cies appeared only in winter, while others were confined 

 exclusively to the summer. A closer investigation of 

 these insects has convinced me that each of the summer 

 species is identical with one of the winter species. My 

 grouping of them is as follows : — 



Wet season form. Dry season form. 



(1.) Precin ceryne, Boisd. = Precis tukiioa, Wallg. 



(2.) Precis aiiiiia, Wallg. = Precis cuama, Hew. 



I Precis sesamus, Trim. 

 (3.) Precis octctira, Cram. = -' „ ■ . • t\ 



^ ■' IPr-ecis amestr/s, Dvury. 



Dry season form. Wet season form. 



{ Precis 2^elasfjis^ God. 

 (4.) Precis archesia. Cram. = j „ . , ^t 



^ ■' ' ( Precis cnapunga, Hew. 



(5.) Precis arfaxia, Hew. = Precis nachtiffalii, Dew. 



In P. naiaVica, Feld., P. fugeJa, Trim., and P. elgiva, 

 Hew., the seasonal forms are not nearly so marked, and 

 they have, therefore, not been separated. As regards 

 P. sopJiia, Fab., which can hardly be considered as a true 

 South African species, the West Coast variety mentioned 

 by Trimen (S. AL But., vol. i., p. 221) will doubtless 

 prove to be its dry season form. 



The alterations exhibited in this genus are of special 

 interest, not only on account of the great differences in 

 the colouring of their two forms, but also because 

 of their marked change in habits, and a study of them 

 might give us a clearer insight into the true cause of 

 dimorphism. 



The general lines on which the variation runs in the 

 genus is as follows : — 



The dry season form is smaller, and usually assumes a 

 duller type of colouring on the upper side, sometimes of 

 quite a different hue; the underside becomes of a general 

 brownish tint, more or less resembling a withered leaf, 

 the likeness being heightened by an oblique line running 

 from the apex of forewing to the anal angle of hindwing 

 representing the midrib ; also l)y the marked pro- 

 longation of the forewing, so well known in the winter 

 form of Melaniti's leda. Lastly, the ocelli on the under- 

 side are much reduced or obsolescent. 



