( 105 ) 
V. Seasonal Dimorphism in African Butterjlies. By 
Arruur G. Buruer, Ph.D., F.L.S., etc. 
[Read February 3rd, 1896. ] 
Mr. Guy A. K. Marsuatu’s “Notes on Seasonal 
Dimorphism in South African Rhopalocera” (Trans. Hnt. 
Soc. Lond., 1896, p. 551), as observed by him in 
Mashunaland, are of great interest and form a contribu- 
tion to science which will be very useful to future workers, 
as exhibiting a part of the truth relating to this engross- 
ing subject; but a part only, as it is now my object to show. 
Mr. Marshall has evidently misunderstood my remarks 
respecting seasonal and local modifications of species ; 
he has indeed wholly missed my point, which is this :— 
in a country which is hot and dry throughout the year 
wet-season forms will be naturally extremely rare (if 
present at all), whereas the reverse will be the case in an 
uniformly moist climate. Now where a species ranges 
throughout Africa to Arabia, it exhibits in one locality 
a single type (say dry-season), and perhaps in abnormal 
seasons when light showers fall, a second type (inter- 
mediate between dry and wet); or if the country be 
moist a wet-season and an intermediate-season form 
occur, but no dry-season form. Such is frequently the 
case in Sierra Leone. 
In countries where the wet season is out of all propor- 
tion to the dry, the wet-season form of a species will be 
naturally better marked ; and the reverse will hold good 
where the dry season has the advantage. 
It is very likely that Mr. Marshall may be correct in 
his opinion, based upon practical experience in Mashuna- 
land, that, in Acrea, I have called the dry-season form 
‘“‘wet,’ and the wet-season form “dry,”’* but I am 
* He however makes an exception in the case of A. bomba (= 
indunda). 
TRANS, ENT. Soc. LOND. 1897.—PaRTI. (APRIL.) 
