Pycnomerinx Hull, 1962

Londt, Jason G. H., 1990, Afrotropical Asilidae (Diptera) 20. The genus Pycnomerinx Hull, 1962 (Stenopogoninae), ANNALS OF THE NATAL MUSEUM 31, pp. 19-32 : 21-22

Pycnomerinx Hull, 1962

Pycnomerinx Hull, 1962:145 .

Type species: Pycnomerinx annuialus Hull, 1962 (= Habropogon rhodesii Ricardo, 1925 ), by original designation.

Hull (1962) stated that Pycnomerinx is 'Related to Scylaticus Loew from which it is separated by the rather long though slender microsegment attached to the long, slender, third antennal segment, which is much shorter than in Scylaticus and more slender; also by the dense and quite long and extended mystax of the facial gibbosity and by the unusually long, large, swollen palpus. Second segment of the palpus densely covered below with long, coarse, bristly pile. First segment of all of the tarsi quite short, especially on the first four legs.' In my view the antennal differences alluded to are unconvincing in the light of variation within the two genera under discussion. The palpal characteristics are, however, diagnostically valuable. Heads dissected and cleared show only a single well-developed palpal segment ( Figs I, 4 ). The fact that this segment lacks the terminal pit and internally associated 'gland' (present in most genera of the subfamily) suggests that Pycnomerinx may lack completely the second palpal segment. The overall length of tarsomeres are somewhat shorter than in Scylaticus but lengths of individual tarsomeres relative to each other do not show marked differences. In his key (couplet 55A), Hull (1962) also points to differences in the setation of the scutellar margin; Scylaticus having ' 1 or 2 pairs of bristles' while Pycnomerinx has the 'whole posterior margin of the scutellum with an extensive, dense fringe of long bristles and bristly hairs'. The significance of this apparently good character will only be fully appreciated when a study of Scylaticus is completed. In the same couplet Hull also draws attention to a difference in venation; Scylaticus having the 'fourth posterior cell [cell m3] generally narrowed to half its maximum width' while Pycnomerinx has this cell 'open in its maximum width'. A preliminary assessment indicates that the genera do not demonstrate a clear difference with regard to the shape of cell m3 but again the importance of this feature will only be properly appreciated after a revision of Scylaticus has been done. For the time being I consider that the single-segmented palp represents the most reliable synapomorphic character for Pycnomerinx . The somewhat downturned, bow-shaped form of the labium ( Fig. 1 ) also appears to be a potentially useful diagnostic feature of Pycnomerinx (as mentioned and illustrated by Oldroyd (1974)).

Key to the species of Pycnomerinx Hull

1 All mesonotal microsetae yellowish, no darkly coloured ones present ........ rhodesii (Ricardo, 1925)

Mesonotum with a number of dark red-brown to black microsetae...... .. 2

2 Antennal macrosetae dark red-brown; T3 entirely fine pruinose (golden in cJ', silvery in 2); wing membrane without slight staining adjacent to certain veins ................................... " gweta Oldroyd, 1974

Antennal macrosetae white or pale yellow; distal half of T3 silver pruinose (proximal half shiny black); wing membrane frequently with yellowish staining along certain veins ............................ cogani Oldroyd, 1974

Figures

Figs 1-6. Pycnomerinx rhodesii Ricardo. 1-2. Head aspects. 1. Lateral. 2. Dorsal. 3. Outer view of right antenna. 4. Right palp. 5. Winll. 6. Prosternum, anterior aspect. (1 -4 & 6- Skukuza cf; 5-25 km W of Windhoek 0"). Scale Jines = I mm.