( brii ) 



T. achine, Cram., and T. auxo, Luc, all taken by us in those 

 localities during August and September of the present year. 

 Wherever possible, I have included the male and female of 

 both the Natal and the Rhodesian form of each species 

 exhibited. I also show, for comparison, male and female 

 specimens of the same four species, taken in the same localities 

 as our own, but during the wet season of the year instead of 

 the dry. As none of the specimens exhibited was selected for 

 the purpose of proving any point, but each is a fair repre- 

 sentative of the category to which it belongs, the whole 

 assemblage may be taken as an illustration of the general 

 correspondence of the variation of these particular forms with 

 the meteorological conditions prevailing at the time of year 

 when they are respectively found. So different in appearance 

 are the 'wet season' and 'dry season' phases of these butter- 

 flies, that, as has also happened in many other cases, they 

 have been described under different names, and are even now 

 pretty generally ranked as separate species. It may therefore 

 not be amiss to recall the fact that in the case of three out 

 of the four it has been absolutely proved by Mr. G. A. K. 

 Marshall, who has bred them through, that the two seasonal 

 forms are conspecific (see Trans. Ent. Soc. Lond., 1902, 

 pp. 200, 209-212). 



" There remain two further points that seem worthy of 

 note. One is that, as will be easily evident on inspection, 

 our Natal forms, though distinctly of the 'dry season' type, 

 are appreciably less extreme in that direction than are our 

 Rhodesian representatives of the same species. This corre- 

 sponds with the much more markedly dry meteorological 

 conditions that we found prevailing in the latter locality. 

 The other point is that, even in cases where the wet-season 

 males of two species, such as T. omphah and T. achine, are 

 quite unlike one another, the resemblance between the dry- 

 season males of the same two species may be so close that 

 in the field they can only be distinguished with difficulty." 



Colonel J. W. Yerhuiu* said that in his opinion the term 

 "seasonal" when applied to developments of this kind was 

 misleading. The variation of the forms seemed to depend 

 not upon fixed seasonal conditions, wet or dry weather, but 



