Lepidoptera from the White Nile. 155 
FURTHER NOTES ON SEASONAL DIMORPHISM, SUGGESTED 
BY THE ABOVE COLLECTION. 
It will have been noticed that Mr. Loat’s specimens fall 
roughly into three series; the first (4) consisting of the 
butterflies captured near Kaka from April 13 to April 21, 
1901; the second (#) comprising those collected at 
Mangala and Gondokoro from Jan, 8 to Jan. 18, 1902; 
and the third (C) being the final batch from (ondolern 
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 
ull three series to show a preponderance of dry-season 
forms, though some specimens in series 4 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 Zerias brigitta are 
both wet-season forms; and the same series (/) contains 
several wet-season examples of Delenois mesentina aud one 
of B. severina. But the most curious instance of apparent 
seasonal irregularity occurs in the case of Zeracolus 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 dimorphic species—Myr. G. A. K. Marshall has 
lately drawn attention to the fact that in the genus Acrwa 
“where the summer males exhibit any particular brilliancy, 
as petra, 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. 
