96 



AFRICAN MIMETIC BUTTERFLIES 



But in the absence of fuller data and further specimens, we can hardly argue any- 

 thing of prime importance from these two isolated examples. In his Presidential address 

 to the Entomological Society in 1898 Trimen described a form of female cenea from 

 Zanzibar which was much less modified from the male than even the form dionysos, 

 and which appeared to be a reversion to the original colour of the female. Some years 

 later several examples of this variety were received from Kikuyu Escarpment, and the 

 form was described by Professor Poulton,^ who gave it the name of trimeni. It is one of the 

 females of the subspecies dardanus polytrophtis (R. and J.). The example I have figured 

 on Plate X is now in the Hope Department at Oxford. It will be noted that the ground- 

 colour is less modified from that of the male than in any of the other varieties, whilst the 

 somewhat indeterminate nature of the darker markings on the fore-wing exhibits a perfect 

 transition between the general appearance of the males of the group and that of the hippocoon 

 form. This transition is very beautifully shown in the series of examples of polytrophus 

 in the museum referred to. The specimen figured is nearest to the male in colour and pattern. 

 In the next specimen the dark areas are much blacker and more definitely outlined, whilst in 

 a third example the pale sub-apical bar and the broad black hind-wing margin are still more 

 clearly marked. In a specimen of the hippocoon variety of this subspecies the principal 

 change is that of the ground-colour which is now white, and the darker areas are brownish 

 rather than black. From this point we get, on the one hand, the definite hippocoon form 

 by the blackening and stronger definition of all the dark areas, and, on the other hand, the 

 cenea form by the separation of the sub-apical bar into spots and the extension of the black 

 area along the inner-margin of the fore-wing. Fig. 15 shows a specimen intermediate 

 between Fig. 3 and the cenea variety, the latter being very simply produced by the whitening 

 of the spots in the fore-wing and the darkening of the yellow of the hind-wing basal area. 

 There are also in this series two extremely interesting intermediate specimens, one being 

 like the advanced form of trimeni^ but with the whole of the ground-colour reddish-yellow, 

 like trophonius, whilst the other has paler reddish basal areas in both wings and the spots 

 of the ancestral pale buff colour. It will be noted that the example of trimeni figured on 

 Plate X shows the rudiment of a tail in the hind- wing in the same way as does the specimen 

 of hippocoon at Fig. 5. 



The next female variety is that described by Trimen,^ and named planemoides. The 

 example exhibited at the meeting of the Entomological Society in October of 1903 was 

 taken in Uganda, and the only other then known specimen was taken in 1873 in Angola. 

 This form is a wonderful mimic of Planema poggei (Dewitz), an insect which acts as a model 

 for so many butterflies in the neighbourhood of Entebbe. A specimen is figured on Plate X, 

 Fig. 12. The resemblance of the Papilio to the Planema had already been recognized by 

 Neave, who worked out the larger collection in which it was included. Planemoides presents 

 a somewhat striking departure from the other varieties, as will be seen from the figure. 

 It is interesting and important to observe that this form only occurs in the same regions 

 as the Planema which it imitates, the variety not having been found to occur in the other 

 subspecies of dardanus. The form has not hitherto been bred from the ova, so that actual 

 proof of its affinity was not at first forthcoming. That proof was obtained in a very singular 

 and unexpected manner. An example was taken by Behrens in 1902-3 on the west shore 

 of Lake Victoria Nyanza, near Entebbe, and was described and figured by Professor Poulton 

 in the Transactions of the Entomological Society in 1906. It proved to be a gynandro- 

 morphous specimen, the left wing exhibiting a considerable portion of the male colour and 

 ^ Trans. Ent. Soc, p. 283, 1906. 2 Proc. Ent. Soc, 1903, p. xxxviii. 



