Lcpidoptcra from, tli.e JVhite N'ile. 155 



Further notes on Seasonal Dimorphism, suggested 



BY the above collection. 



It will liave been noticed that Mr. Loafs specimens fall 

 roughly into three series; the first (A) consisting of the 

 butterflies captured near Kaka from April 13 to April 21, 

 1901 ; the second (B) comprising those collected at 

 Mangala and Gondokoro from Jan. 8 to Jan. 18, 1902 ; 

 and the third (C) being the final batch from Gondokc^ro 

 caught on March 8, 1902. From the accounts that have 

 been given above of the meteorological conditions prevalent 

 at these periods in the several localities, we should expect 

 all three series to show a preponderance of dry-season 

 forms, though some specimens in series A might exhibit 

 the influence of the early rains. The facts are well in 

 accordance with this expectation, but it will be seen that 

 series B, though belonging in point of time to the height 

 of the dry season, affords examples of the statement that 

 " in many cases where the existence of seasonal modifica- 

 tion has been reasonably presumed, or even actually 

 demonstrated, the seasonal relation is far from being 

 rigidly fixed." * 



Thus, the two January specimens of Tcrias lirigitta are 

 both wet-season forms ; and the same series (i>) contains 

 several wet-season examples of Bclcnois mcsentina and one 

 of B. sever ina. But the most curious instance of apparent 

 seasonal irregularity occurs in the case of Teracolus daira. 

 All the specimens of this form caught at Mangala on Jan. 

 8 and 9 are heavily marked on the upper surface, and 

 would certainly be pronounced at once by most authorities 

 to belong to the wet season. Those on the other hand 

 taken near Kaka on April 21, when the rains had well 

 started, are lightly marked, and bear all the appearance of 

 dry-season examples. Facts of this kind help to emphasise 

 the need that exists for still fuller and more accurate data 

 than we at present possess, if the problems of seasonal 

 dimorphism are to be satisfactorily unravelled. 



Persistence of dry-season coloration in the females of 

 seasonally dimorijliic species. — Mr. G. A. K. Marshall has 

 lately drawn attention to the fact that in the genus Acnva 

 " where the summer males exhibit any particular brilliancy, 

 as petrivOj, atolmis, or nohara, it is always compensated for 

 by an exceptional dulness on the part of their respective 



* Trans. Ent. Soc. Lond., 1902, p. 193. 



