Section D.— Bradford, 1900. 



( 2. ; Observations on Mimicry in South African Insects. 

 By Guy A. K. Marshall. 



[Arranged and Communicated by Edward B. Poulton, M.A., F.R.S. Fellow of 

 Jesus College, Oxford, and Hope Professor of Zoology in the University.] 



The following paper is an abstract of the results obtained by Mr. Guy A. K . 

 Marshall in South Africa. When no locality is mentioned it is to be understood 

 that the observation was made at Salisbury, Mashonaland (5,000 feet). The 

 observations here briefly recorded have added in a most important manner to our 

 knowledge of the natural history (bionomics) of South African insects, a subject of 

 which the foundations were laid by Roland Trimen. Groups of mimetic Lepido- 

 ptera captured on the same day as their models have been obtained both from Natal 

 and Mashonaland (Salisbury), thus demonstrating more fully than has been done 

 hitherto the fact that model and mimic fly at the same time as well as in the same 

 place. The groups bring out the extraordinary power of Danaine butterflies in, so 

 to speak, moidding the species of other sub-families into a superficial likeness to 

 themselves. There are only four or five species of Danaince in the region under 

 consideration, and each one of them is the centre of a gi-oup of forms superficially 

 similar, but remote in afiinity. The abundant and widespread Limnas chnjsippus 

 was largely resembled both in Natal and Mashonaland. In experiments conducted 

 upon insect-eating animals, this butterfly appeared to be less unpalatable than the 

 Acrcea {A. encedon) which resembles it. The explanation may be found in the far 

 wider range of the Danaine model, which would render it familiar to enemies 

 passing from an area in which the Acrma does not, to one in which it does exist. 



In the case of two forms of Euralia (E. mima and E. tvahlbergi) mimicking two 

 very diflerent species of Amauris {A. echeria and A. dominicanus) there is good 

 reason to believe that a single species has become dimorphic. Photographs of 

 four mima (two male, two female) and four wahlhergi (three male, one female) were 

 shown, the whole set having been part of a company of twelve individuals going to 

 rest together on a small clump of fern under a steep kraantz, Umbilo River, 

 Malvern, near Durban, Natal (June 28, 1897). The two forms have also been 

 taken in coitu, and have been found together freshly emerged from the pupa on the 

 same tree. Intermediate varieties are also known. If specific identity be established, 

 the case will constitute a new form of mimetic dimorphism in the Lepidoptera, 

 similar to that of the Dipterous genus Vvlucella. All cases of dimorphism in mimetic 

 Lepidoptera hitherto described are either sexual or confined to a single sex. In one 

 sex, indeed, a mimetic species may be polymorphic, as in the female of Papilio 

 cenea or Hypolimnas misippus. 



In the case of the distasteful sub-family Acrceince, the two very different 

 species A. nataUca and A. anemosa were shown captured at Salisbury on the same 

 day. Although entirely different in detail, the pattern of the two species is broadly 

 the same, and during flight would probably appear to be identical. Another even 

 more striking example of Miillerian or synaposematic resemblance was afforded by 

 a set of eighteen specimens belonging to five species of small Acrseas captured on 

 the same day (December 31, 1898) in the same locality. The whole group pre- 

 sented a wonderfully uniform appearance in size, shape, colour, and the general 

 distribution of markings. 



An example of a Hesperid {Baoris netopha) mimic of an Acr(ea {A. double- 

 daiji), the two captured on the same day, added another to the rare instances of 

 mimicry in this family. The resemblance is only seen in the attitude of rest, 

 and is confined to the undersides of the wings. 



d\2 



