1897.] BUTTERFLIES OF THE GENUS TEEACOLUS. 5 



21 occur in the South-African subregion (the northern boundaries o£ 

 which are the Zambesi E. and Cuneue E. on the East and West 

 Coast respectively) and 5 of them are restricted to it. In the 

 Oriental region as many as 8 out of the 19 species are not found 

 further east than Arabia. 



In any attempt to differentiate the species of Teracolus, or indeed 

 of any other genus of Butterflies, tw o important facts must always 

 be kept in view : firstly, the strong tendency of these insects to 

 develop more or less marked local variations consequent upon the 

 diii'erent conditions of their environment in different localities ; and 

 secondly, the phenomenon of seasonal dimorphism, owing to which 

 the same species may present a strikingly different appearance at 

 different times of the year, more especially in those countries whose 

 climate is marked by well-defined wet and dry seasons. In dealing 

 with local variation the general rule that 1 have laid down for 

 myself is, that when two local forms exhibit a gradual mergence into 

 oiie another so that intergrades occur which might be attributed 

 to either of them, then those two forms constitute a single species. 

 As an example I may refer to T. evagore, Klug. This is a North- 

 African form which is represented in the West and South by the 

 very different looking T. pUegetonia, Boisd. But throughout 

 Central Africa we get the admittedly variable form T. minans, Butl., 

 which shows beautifully the gradual cliange from T. phlegetonia to 

 T. evagore, and I have therefore grouped them together, regarding 

 the latter as a dwarfed and under-coloured climatic variety of the 

 former, to which it is closely linked by a number of other so-called 

 species. On the other hand, in the island of Socotra there is 

 T. nivens, Butl., which is in every way far more like T. evagore %\i?t.n 

 is T. phlegetonia ; but the shght characters which distinguish it are 

 quite constant (it being confined to the island), and therefore I 

 regard it as a distinct species. 



With regard to seasonal dimorphism, without a certain amount 

 of field experience it is usually difficult to decide what may be the 

 dry-season form of any given wet-season specimen and vice versa ; 

 but the following general rules may give some idea of the seasonal 

 modifications in Teracolus. 



The dry-season form usually differs from that of the wet-season 

 in the following respects : («) its smaller size ; there are, however, 

 several species, such as T. faustus, calais, and protractus, in which 

 the dry form is not reduced ; (b) when there is any difference in the 

 shape of the fore wing, that of the dry form is always more acute ; 

 (c) the reduction or complete absence of many of the black mark- 

 ings : in groups like T. achine and T. evagore this is very noticeable, 

 but apparently it does not hold good in T. Calais, protractus, or chry- 

 sonome and their alUes, for in them the upperside markings do not 

 vary ; (d) the colouring of the underside of hind wings, which is 

 perhaps the most reliable character of all : the white or green under- 

 sides of the wet-season forms assume a yellowish, sandy, or pinkish 

 tinge and become more or less irrorated with fuscous atoms ; the 

 colouring, however, is often very variable in the same species and is 



