84 R. W. CROSSKEY 



exceptionally long (Text-fig. 265). Larval mandible with two serrations, comb-teeth few but 

 long and first three comb-teeth blunt apically (Text-figs. 293, 298) . Larval cuticle bare. End of 

 abdomen bulbously produced to overhang anus and anal sclerite. 



This group contains only the single species lumbwanum de Meillon, but it is 

 possible, as Freeman & de Meillon (1953 : 129) have pointed out, that the species 

 known under this name may be a compound of two species (or possibly more) . The 

 characters of lumbwanum taken together, but in particular the extraordinary pupal 

 abdominal onchotaxy with its girdles of irregularly arranged hooks around the fifth 

 to eighth segments (not found in the same form in any other Simuliam), make it 

 impossible to assign the species satisfactorily to either the berneri-group or the 

 copleyi-group and a monospecific group on its own is necessary for it. It resembles 

 the berneri-group in having a well formed parameral hook each side in the male 

 hypopygium and in the larval cephalic fans, but resembles the copleyi-group more 

 closely in having the larval cuticle bare (although a few specimens, apparently of 

 lumbwanum, have been seen in which the posterodorsal part of the cuticle shows a 

 few colourless papilliform prominences) . 



The larval cephalic fans of lumbwanum form when open a curved brush similar in 

 shape to that of all typical forms of Simulium, but the rays composing the fan are 

 exceptionally slender and appear to lack a filter apparatus ; this, although in fact 

 present, is so delicate that it is difficult to make out its structure even with phase- 

 contrast examination. Exactly similar long very narrow rays with almost invisible 

 filter apparatus occur also in the cephalic fans of the berneri-group, and the two 

 groups together therefore have a very different type of feeding organ from that 

 occurring in the copleyi-group (as described under this group heading below). The 

 functional significance of this difference is not yet clear. 



The lumbwanum-gr oup is known mainly from Kenya, but occurs around Mount 

 Elgon in eastern Uganda. Corbet (1960a) recorded lumbwanum from Ripon Falls on 

 the Victoria Nile in Uganda and material on which this record is based is in the 

 British Museum (the identity is confirmed) : it is now probable, however, that 

 insecticidal operations in the Victoria Nile have eliminated lumbwanum from 

 this site. A single pupa of the species (in B.M. collection) is known from the 

 Victoria Falls on the Zambesi River. The distribution, as at present known, does 

 not appear to overlap with that of the berneri-group which has a more westerly 

 distribution, and is associated with Elassoneuria mayflies : the lumbwanum-gr oup 

 is only known to be associated phoretically with mayflies of the genus Afronurus 

 Lestage (Ephemeroptera : Heptageniidae) . At least two species of Afronurus {A. 

 ugandanus Kimmins and A . peringueyi (Esben-Petersen)) act as carriers of immature 

 lumbwanum, but there are probably others since many nymphs of Afronurus involved 

 in the associations cannot be identified to species with certainty. 



Included taxon. Simulium (Phoretomyia) lumbwanum de Meillon ; possibly also 

 unrecognized semi-sibling species confused under this name. 



copleyi- group. Fore tarsus enlarged (except diceros) and basitarsus 4-5 times as long as its 

 greatest width, with dorsal hair crest (Text-fig. 81). Postnotum sometimes with patch of pale 

 yellow to golden scales on each side. Scutum evenly covered with golden scales. Abdomen 



