Stenobasipteron Lichtwardt, 1910

Barraclough, David A., 2006, An overview of the South African tangle­veined flies (Diptera: Nemestrinidae), with an annotated key to the genera and a checklist of species, Zootaxa 1277, pp. 39-63 : 52-53

Stenobasipteron Lichtwardt, 1910

Stenobasipteron Lichtwardt, 1910: 614 . Type species: Stenobasipteron wiedemanni, Lichtwardt, 1910 , by designation of Bernardi (1973: 259).

wiedemanni Lichtwardt, 1910: 614 . Eastern Cape; KwaZulu­Natal.

Discussion: Stenobasipteron species are moderately sized to large flies, typically unicolorous or virtually so, ranging in length from 10 to 18 mm. They typically differ from Moegistorhynchus and Prosoeca in having a more slender facies ( Fig. 3 ). Proboscis length ranges from about 10 to 20 mm. The very striking anterior costal flexure of the wing in males of S. wiedemanni ( Fig. 8 ) is the most prominent in the South African Nemestrinidae , although less prominent character states of this sexually dimorphic character occur also in other Stenobasipteron species and in some species of Prosoeca .

Barraclough (2005b) reduced the number of species in Stenobasipteron from five to three, after transferring two species to Prosoeca (see discussion under Prosoeca ). Of the three remaining species, S. wiedemanni is the only species recorded with certainty from South Africa. Bowden (1980) recorded it from Zimbabwe as well, but based on my review of available material, S. wiedemanni is a South African endemic. Stenobasipteron gracile Lichtwardt, 1910 , originally described from Zimbabwe, was recorded from South Africa and Malawi by Bowden (1980), but I cannot confirm the South African record, and the Malawi record is unlikely. Stenobasipteron arnoldi Bequaert, 1925 a, also described from Zimbabwe, has not been identified in any South African material of Stenobasipteron that I have seen.

Although I have recorded only one described species of Stenobasipteron from South Africa, several undescribed species are represented in the northeastern provinces of Mpumalanga and Limpopo (Barraclough, in prep.). It appears that Stenobasipteron has speciated extensively in the eastern part of Southern Africa and is represented also in Swaziland and western Mozambique.

The habitat preference of Stenobasipteron is perhaps of more interest than that of other genera of Nemestrininae, in that the commonest species, S. wiedemanni , is thought to be restricted to forests or closed­canopy habitat (e.g. C.J. Potgieter & Edwards 2005). This is unusual in the Nemestrinidae , although I have often encountered Prosoeca species in sunlit patches at forest margins. In Mpumalanga and Limpopo, Stenobasipteron species occur in other habitats as well, including grassland and savanna.

Potgieter & Edwards (2005) described a separate pollination guild centred on S. wiedemanni . S. wiedemanni was previously considered part of the P. ganglbaueri guild ( Goldblatt & Manning 2000). However, the new guild refers to a species complex and not just S. wiedemanni , as the Stenobasipteron specimens from Mpumalanga and Limpopo, cited by Potgieter & Edwards (from Goldblatt & Manning 1999 2000) as S. wiedemanni , are in fact a number of undescribed species ( Barraclough 2005b). Potgieter & Edwards record S. wiedemanni as a pollinator of 19 plant species in six families: Acanthaceae , Balsaminaceae, Gesneriacae , Iridaceae , Lamiaceae and Orchidaceae . Some of these records in Mpumalanga and Limpopo (e.g. for Orthosiphon tubiformis ( Lamiaceae )) refer to an undescribed Stenobasipteron species. This accounts for the divergent ecology referred to by Potgieter & Edwards (2005: 263), i.e. the guild operating in grassland in Mpumalanga, as opposed to closed­canopy forest elsewhere.

Relationships: As already discussed under Prosoeca , Stenobasipteron is very closely related to Prosoeca . The generic concept is provisionally upheld, pending further study.

Figures

FIGURES 2 – 4. Adult flies in the field. 2. Moegistorhynchus longirostris visiting Laperouisia anceps (Cape west coast) [C. Paterson­Jones]. 3. Stenobasipteron wiedemanni visiting Isoglossa sp. (KwaZulu­Natal) [G. Upfold]. 4. Atriadops species at rest (Mpumalanga) [M. Picker].

FIGURES 5 – 8. Wings of Nemestrininae. 5. Moegistorhynchus longirostris, showing apical reticulation and divided fifth posterior cell at posterior margin. 6 – 7. Species with characteristic patterning. 6. Prosoeca peringueyi. 7. Prosoeca ganglbaueri complex. 8. Stenobasipteron wiedemanni, male.