Notes on Seasonal Dimorphism. 555 



clearly exhibit seasonal variation along tbe normal lines. 

 This has been quietly ignored by Mr. Butler, who has 

 thereby fallen into the very error against which he warns 

 ns later on, viz. : that of confusing local with seasonal 

 variation. 



As the dimorphic forms in this genus seem to have 

 been so misunderstood, perhaps a few remarks on other 

 South African species may not be misplaced : — 



Acrwa asema, He\^. The bright coloured, strongly 

 spotted summer form is replaced in winter by a duller 

 form, in which the black markings are reduced, the two 

 upper spots in subapical row usually being obsolete, and 

 very nearly the whole now is absent. 



Acrfea aglaonica, Westw. Trimen, in discussing 

 Selous' specimens of this species (P. Z. S,, Jan. 16, 

 1894) refers to some of them as constituting rather a 

 striking variety in the direction of A. natalica, Boisd. 

 These are undoubtedly examples of the summer form, 

 which differ from the typical winter form in having, as 

 usual, all the black markings on the upper side very 

 strongly developed. But the most noticeable difference 

 is the disappearance of the peculiar transparent subapical 

 patch, a form of seasonal variation without parallel in 

 South Africa. 



Several species, such as A. petrxa, Boisd., A. raliira, 

 Boisd., and A. douhledayi, Guer., vary very markedly in 

 the ground-colouring of tbe ? ; but I need only cite the 

 most noticeable example, viz. : — 



Aciwa halali, n. sp. This species was first taken by 

 Mr. F. C. Selous on the Manini and Vanduzi Rivers, 

 between Umtali and Chimiro, and I have since taken it 

 very abundantly about Salisbury. Trimen considers it to 

 be merely a slight variety of the southern A. nohara, 

 Boisd.; but if A. asema, Hew., be considered distinct 

 from A. violarnm, Boisd. (which it is, in my opinion), 

 there is even still more reason for separating halali from 

 nohara. The description of the insect is as follows : — 



S Wet season form. Bright brick-red, with a strong 

 pink tinge in hindwings, especially towards base. Spots 

 and markings of the same general pattern as in A. nohara, 

 Boisd., but very much reduced, so as to give the insect a 

 markedly difierent appearance ; moreover, it differs con- 

 stantly in the complete absence of the discal spot below 

 first median nervule in forewing, and the third and fifth 



