Tlie Bionomics of South African Insects. 417 



Hist, ser, 7, vol. ii, July 1898, p. 80), which it is only 

 just to describe as epoch-making in the history of seasonal 

 dimorphism, Mr. Marshall recorded this great discovery, 

 and published the fact that he had succeeded in breeding 

 sesamus from natal cnsis in three cases. Tlie specimens 

 themselves Mr. Marshall presented in two cases to the 

 Hope Collection at Oxford, in the third to the British 

 Museum of Natural History. The Oxford specimens are 

 figured on Plate XII, figs. 1 and 2 the parents, figs. \a, Ih, 

 and 2« the offspring. The dates of the various stages are 

 given in the description of the plate. 



These specimens must always have historic interest, and 

 I have therefore published in the plates accompanying 

 this memoir a representation of the whole of the evidence 

 obtained by Mr. Marshall in 1898, so far as it is at my 

 disposal. The extracts from Mr. Marshall's letters bearing 

 on the same subject have also historic interest, and are 

 therefore recorded in full below. 



" Umhomaas Mouth, Natal ; Sept. 3, 1897. — I am sorry 

 to say I have never yet bred natalcnsis through to sesamus. 

 At Karkloof, Natal, I managed to secure three eggs in 

 March (just the right month for the purpose of testing 

 the hypothesis that they are the same species), and one of 

 the resulting larvj3e was fully half-grown when I left there 

 for Malvern, near Durban. I brought them down with 

 me, as I knew that C. N. Barker had bred 7iata!cnsis from 

 the larva, and so would know their local food-plant. The 

 Karkloof plant does not occur at Malvern, and the larvse 

 utterly refused the Malvern food-plant and everything 

 else I tried them with; so they pined away and died. 



" I have not the least doubt of the specific identity of 

 these two forms ; they are undoubtedly confined respec- 

 tively to the wet and dry seasons, they have been frequently 

 observed in coitu, and intermediate forms occur at tlie 

 change of seasons. The larvse are identical and feed on the 

 same plant ; for out of twelve larva; taken by Hutchinson 

 off one plant, ten were natalcnsis and two sesamus. I 

 always think natalcnsis is an interesting species as showing 

 the brilliant colours which can be acquired by an unpro- 

 tected species without detriment. A newly-emerged 

 natalcnsis is a glorious insect, and rivals the brightest 

 Acrajas in its colouring on both surfaces ; moreover, it is 

 a frequenter of open country, where its salmon-red wings 



TRANS. ENT. SOC. LOND. 1902. — PART III. (NOV.) 28 



