The Bionomics of Sontli African Insects. 433 



fishers, etc., and owing to the warmth of the midday sun, 

 even in mid-winter, the lizards are always more or less 

 active, and the insectivorous mammals are probably in no 

 way reduced. With the insects it is very different ; owing 

 to the parching up of the vegetation the hosts of phyto- 

 phagous insects disappear almost entirely, and the diminu- 

 tion in insect-life is enormous, being most noticeable 

 among the Coleoptera and least so among butterflies, of 

 which latter almost two-thirds have winter broods ; and 

 moreover their lives would be rendered even more pre- 

 carious by the generally adverse conditions of their 

 environment from climatic causes. It therefore seems 

 clear that the struggle for existence would fall pretty 

 severely on butterflies during the winter, owing to their 

 general conspicuousness, and that such is actually the case 

 is shown by the numerous instances of the development of 

 a highly-protective under-side coloration during the dry 

 season among S(ityrini&, Nymphalina?, Lycxnidm, and 

 PicriniB. That the struggle is sufficiently keen, however, 

 to compel unpalatable species to adopt protective color- 

 ation I should not like to say. The following is, I take it, 

 a complete list of the South African genera possessing 

 more or less undoubted distasteful qualities : Limnas, 

 Amauris, Ac'}\tm, Flancmct, Fardcpsis, Ncptis, Peniila, 

 Alasna, MyJothris, and Pontia heUiccc, and with the ex- 

 ception of AcTcva none of these exhibit any change of 

 colour during the winter which can possibly be construed 

 as protective. Dealing therefore with Acrnm, I find that 

 even in this genus a considerable number of species such 

 as horta, neohule, anemosa, acarci, cnrcdon, cabira, etc., 

 exhibit only a comparatively insignificant seasonal dimor- 

 phism or even none at all. There remains therefore a group 

 composing such insects as violarum-ascma, nohara-halali, 

 petrma, doiihlcdayi-axina, atolmis, huxtoni, etc., in which the 

 dimorphism is fairly strongly maiked in one sex or the 

 other, and an interesting feature about this group is that 

 they are all, with the exception of ]^)etr!va, frequenters of 

 open country, having a low flight and frequently sitting on 

 the ground. It is also noticeable that this group, unlike the 

 other, presents a very marked difference in the sexes, and 

 wherever this is not the case, both sexes have a distinctly 

 obscure coloration as compared with their congeners, e. ^. 

 axina and asnna ; further, that where the summer males 

 exhibit any exceptional brilliancy, as petrsea, atolmis, or 

 TRANS. ENT. SOC. LOND. 1902. — PART Til. (NOV.) 29 



