448 



Mr. G. A. K. Marshall on 



The succession of the seasons is very different, in the 

 region in which Mr. and Mrs. Hinde captured the butter- 

 flies, from that which obtains in Salisbury. The two 

 forms of succession are shown in parallel columns below. 



BRITISH EAST AFRICA 

 (MACHAKOS, KITUr, ETC.). 



MASHON ALAND 

 (SALISBXTRY, MAZOE, OADZIMA). 



Mid-Oetober 



to , 



Mid-December ■' 



to 

 Mid-Marcli 



to 

 end May 



to 

 Mid-October 



■\ Small wet season 

 V (about 17—18 



inches), 

 j- Small dry season. 



^ Big wet season 

 [ (about 17—18 

 -' inches). 



(Big dry season. 



Early November ^ AVet season, aver- 

 |_ age rainfall of 

 j Salisbury about 

 J 3 



to 



Mid- April 



to 



Early November 



S.'i inches. 



■ Dry season. 



It is to be observed that the rainfall of the small and 

 the big wet seasons are about the same, and also that the 

 country is not really dried up in the small dry season 

 except in unusually dry years. The country is always 

 dried up in the big dry season. 



In spite of these great differences in the seasons, the 

 succession of the phases is wonderfully alike in the two 

 areas, as has been pointed out above. We must conclude 

 that sesamns can produce two seasonal phases annually 

 but not more, so that the small dry season of the north 

 is no more effective in producing the dry phase than the 

 simultaneous wet season of the south. The species is so 

 constituted that it produces a dry phase for the big dry 

 season and a wet phase for the rest of the year, some of 

 the dry-phase individuals being produced some months 

 before the normal change takes place, viz. at and just 

 before the beginning of the chief dry season. The differ- 

 ence between the date at which this great change of 

 seasons takes place in north and south is attended by a 

 corresponding difference in the date at which the wet 

 phase of sesamus gives place to the dry. Both lists are 

 unfortunately wanting at the transition from the big dry 

 season to the wet. There is indeed only a single record 

 for the period between the beginning of June and the 

 beginning of December. Speaking from memory, Mr. 

 Marshall thinks that the break from sesamns to natalensis 



