Nothybus

Lonsdale, O. & Marshall, S. A., 2016, Revision of the family Nothybidae (Diptera: Schizophora), Zootaxa 4098 (1), pp. 1-42 : 10

Species groups of Nothybus

The species other than Nothybus longicollis appear to form a natural group on the basis of the following derived features: ventral half of face silvery tomentose with dark brown glossy protuberance (face flat and with quadrate brown spot in N. longicollis ); scutum with brown ill-defined stripes and/or spots; wing with brown transverse stripe and at least 2 clear and strongly iridescent subapical spots in a lightly clouded apical region, and with fainter, illdefined medial iridescence; surstylus longer than wide; phallapodeme broadly fused to hypandrium; pregonite narrowed apically. Nothybus exclusive of N. longicollis ( Figs 1–4 ) can be further divided into the N. biguttatus , N. kempi and N. sumatranus species groups.

The Nothybus biguttatus group, including only N. acrobates ( Figs 31, 32 ) and N. biguttatus (Figs 33–35), is best characterized by two relatively small, clear subapical spots on the wing, with the spot in cell r4+5 positioned basal to that in cell r2+3. The wing has 3 subapical spots in the remainder of the genus aside from N. longicollis , which has none. The brown transverse band is broadly fused to the dark apical margin through cells r1 to r4+5. The first flagellomere is mostly black, the fore basitarsomere is white medially, and there are black velvety dorsomedial patches on tergites 2–6 (not just tergite 5, which is almost always entirely black velvety). Males of N. acrobates are unknown, but it will be significant to find if these also exhibit the unusual genitalic features of N. biguttatus ( Figs 79–83 ): tergite and sternite 6 large, subrectangular and heavily setose; subepandrial sclerite separate from surstylus (not confluent with entire inner surface); subepandrial sclerite and surstylus both long, narrow, furrowed and with minute or tubercle-like setae apically; pregonite straight, narrow, apically tapering, pale and with one pair of distomedial setae; distiphallus relatively short, with one pair of small laterally produced spines on membranous flaps apically.

The Nothybus kempi group is most readily diagnosed by the clear, iridescent wing spots that form a single straight line across the wing ( Fig. 69 ). Other diagnostic features include a white fore basitarsomere with a dark brown basal band at least as long as the width of the tarsomere, an apically clavate pregonite (narrow in N. procerus ), and a long, ribbon-like distiphallus with an apical swelling from which one pair of relatively short tubules arise. The dark spots on the labellum and wing margin are usually pronounced, and the surstylus is usually relatively wide and short. The five species in this group, including all three Nothybus newly described here, are differentiated by relatively subtle characters including wing venation and patterning, notal and abdominal colouration, and several structures of the male terminalia.

The Nothybus sumatranus species group is characterized by the apically displaced middle (of three) clear wing spot ( Fig. 78 ). The fore basitarsomere is entirely white (not banded), the surstylus is narrow and the pregonite is slender apically. Within this group, N. lineifer and N. triguttatus have the distiphallus ribbon-like on the basal half and divided into one pair of very long, clear tubules apically. Nothybus triguttatus , which is almost entirely yellow, is readily differentiated from the other two darkly pigmented species (see comments for N. lineifer ). The phallus of N. sumatranus is extraordinarily distinctive, being extremely broad and heavily sclerotized, with the thick paired basal ribbons each dividing into one pair of narrower ribbons apically that fuse medially into a dark W-shaped structure with a prominent medial process ( Figs 119–120 ).

Figures

FIGURES 1 – 4. Nothybus longicollis (Walker), Borneo, Sabah; 1 – 2: male and female, © M. Ng; 3 – 4: male (?), female © S. Gaimari.

FIGURES 31, 32. Nothybus acrobates Frey, holotype female; 31: ventral; 32: right lateral. FIGURES 33 – 35: N. biguttatus Wulp, female, photos; 33: dorsal; 34: head, anterior; 35: left lateral.

FIGURES 79 – 83. Nothybus biguttatus Wulp, male abdomen; 79: segment 6 to cercus, ventral; 80: same, left lateral; 81: epandrium, subepandrial sclerite, surstylus, cercus, anterior; 82: ejaculatory apodeme; 83: detail of phallus and pregonite, left lateral.

FIGURES 67 – 78. wings, photos; 67: Nothybus longicollis (Walker), with relevant veins listed; 68: N. biguttatus Wulp; 69: N. kempi (Brunetti), with relevant cells listed; 70: N. procerus spec. nov., holotype; 71: N. kuznetsovorum Galinskaya & Shatalkin; 72: N. cataractus spec. nov.; 73: N. lineifer Enderlein, syntype; 74: N. decorus Meijere [syn. nov. of N. lineifer], syntype; 75: N. lineifer, CNC specimen; 76: N. triguttatus Bezzi; 77: N. sumatranus Enderlein, syntype; 78: N. sumatranus, Thai specimen.

FIGURES 114 – 120. Nothybus sumatranus Enderlein, male abdomen; 114: external components, segment 6 to cercus, left lateral; 115: external components past sternite 8, posterior; 116: external components, segment 6 to cercus, ventral; 117: external components past sternite 8, anterior; 118: ejaculatory apodeme; 119: internal components, ventral; 120: same, left lateral.