Natalimyzidae, Barraclough & McAlpine, 2006

Barraclough, David A. & McAlpine, David K., 2006, Natalimyzidae, a new African family of acalyptrate flies (Diptera: Schizophora: Sciomyzoidea), African Invertebrates 47, pp. 117-134 : 120-123

Family Natalimyzidae fam. n.

Type genus: Natalimyza gen. n.

The following combination of character states should distinguish the Natalimyzidae from all other families of acalyptrate Schizophora:

Fully winged flies with well developed palpus and proboscis; fronto-orbital plate broad, with 2 large reclinate bristles and one or two proclinate bristles; postvertical bristles convergent; face uniformly sclerotised; antennal segment 2 without dorsal slit; arista bare, inserted dorsolaterally on segment 3; prothorax very short, without sclerotised precoxal bridge; metathoracic postcoxal bridge absent; thoracic bristles including the following: normally 4 dorsocentrals, presutural, 1+1 notopleurals, 2 pairs scutellars (basal pair reduced), 2 to 5 upper sternopleurals (no propleural or mesopleural); each tibia with one preapical dorsal bristle; tarsi long and slender; costa unbroken, other veins without macrotrichia; subcosta complete, typically diverging from vein R 1 distally; vein R 2+3 terminating close to end of vein R 4+5; discal, second basal and anal cells complete, the latter two rounded distally; vein A 1 vestigial beyond anal cell; vein A 2 visible well beyond alula, desclerotised; alula moderately developed; pre-abdominal spiracles in pleural membrane; protandrium very asymmetrical, with tergite 6, and sternites 6, 7 and 8 well developed; surstylus fused to epandrium; aedeagus, and particularly its distiphallus, short; female postabdomen simple; cerci separate.

A detailed morphological description is given for Natalimyza , the only included genus.

Genus Natalimyza gen. n.

Type species: Natalimyza milleri sp. n.

Etymology: The family name refers to the Natal Museum, as well as the province formerly named Natal, where significant numbers of this taxon were first discovered and studied.Almost 90% of South African material seen by us was collected in KwaZuluNatal. Gender feminine.

Description: Moderately elongate, rather small flies resembling in habitus such genera as Opomyza Fallén (Opomyzidae) and some Clusiidae , without obvious sexual dimorphism except in postabdomen; cuticle predominantly dull, pruinescent; body colour yellow to brown; wing membrane clear, unmarked.

Head ( Figs 2, 3 ): Vertex rounded, without trace of transverse carina. Each fronto-orbital plate broad, undivided, long, but not reaching ptilinal suture. Face variably presented, ranging from relatively broad and weakly sclerotised (differentiated from peribuccal membrane), to narrowed and barely sclerotised. Hypofacial narrow, not visible in profile below cheek. Ptilinal suture medially transverse, passing closely above antennal sockets, laterally prolonged to terminate near vibrissa. Eye occasionally with inconspicuous ommatrichia. Postvertical bristles convergent, short to elongate. Fronto-orbital bristles complex in arrangement: 2 reclinate or outwardly flexed bristles, the more anterior further from eye margin, a proclinate bristle between anterior reclinate bristle and eye margin, usually a proclinate and incurved bristle near medial margin of orbital plate behind anterior reclinate bristle. Ocellar bristles divergent, usually relatively long. Vibrissa either distinct or little differentiated from a series of variably developed and positioned cheek bristles. Supra-occipital setulae in one transverse fascicle. Antenna with segments 1 and 2 short, latter without dorsal slit; segment 3 discoid; arista inserted dorsolaterally on segment 3; segment 4 desclerotised; segment 5 enlarged, subspheroid; segment 6 slender, bare. Prelabrum (= clypeus) well developed, separated but not distant from face.Palpus elongate, usually with an outstanding terminal bristle. Proboscis usually with large labella.

Thorax: Narrow and rather deep. Prothorax very short and inconspicuous. Prothoracic precoxal bridge absent. Probasisternum usually narrowly oval, always bare. Mesoscutum rather prominently gibbous anteriorly. Scutellum without setulae. Subscutellum weakly to noticeably convex, not much enlarged. Mesopleuron with callus on upper posterior margin. Wing process of pteropleuron without convex ampulla (greater ampulla of J.F. McAlpine 1981). Metepisternum attenuated dorsally (its limits sometimes not easily seen), without setulae. Margin of metathoracic spiracle without bristles or setulae. Metasternum bare. Bristles present: 1 humeral, nearly always 4 dorsocentrals, presutural, 1+1 notopleurals, supra-alar, postalar, usually 1 posterior intra-alar, 2 unequal scutellars, 2 to 5 upper sternopleurals (propleural and mesopleural bristles absent); prescutellar acrostichals occasionally present, albeit reduced. Legs of moderate length and thickness. Fore femur with long posterodorsal and posteroventral bristles; other femora without differentiated bristles. Each tibia with one preapical dorsal bristle; mid tibia with one apical ventral spur (absent on other tibiae). Tarsi slender, subequal in length to tibiae, cylindrical except for the depressed terminal segment; mid basitarsus usually slightly to noticeably shorter than hind basitarsus. Claws stout, of moderate length, usually strongly curved; pulvilli shorter than claws, rather broad, with relatively short hairs.

Wing ( Fig. 4 ): Rather long, with almost uniform covering of microtrichia. Costa not broken or incised, extending to vein R 4+5 or vein M 1, with one dorsal and one ventral costagial bristle near base; on most of length with one anterodorsal and one anteroventral series of bristles, sometimes also some fine irregular hairs, and usually spinules in the anterodorsal series; other veins without macrotrichia. Subcosta distinct throughout, typically diverging from vein R 1 distally. Vein R 2+3 long, so that vein R 4+5 terminates nearer to vein R 2+3 than to vein M 1. Discal, second basal, and anal cells complete. Crossveins r–m and m–cu somewhat approximated; very closely approximated in some species and positioned in basal two-fifths of wing, ranging to more broadly separated in others with crossvein m–cu positioned near mid-length of wing. Vein A 1 unbroken on anal cell, reduced to a desclerotised vestige beyond that cell. Vein A 2 visible beyond alula as a slightly pigmented, curved crease. Alula moderately developed, not sinuate on distal margin, with marginal fringe.

Abdomen: Elongate-ovoid, usually longer than thorax. Tergites 1 and 2 partly separated. Sternite 1 distinct, somewhat sclerotised, without setulae. Preabdominal spiracles situated in pleural membrane close to lateral margin of tergites.

Male postabdomen ( Figs 5–9 ): Tergite 6 asymmetrical, usually short but well developed, setulose, rarely reduced and setulae occasionally absent.Sternites 6 and 7 well developed, asymmetrical, usually partly setulose, sternite 7 broadly joined to the setulose dorsal sternite 8; sclerite probably representing tergite 7 sometimes present on right side. One pair surstyli present, immovably joined to epandrium. Hypandrium very variable in shape and size, often bearing paired spines or groupings of spines, and/or with paired projections, the latter usually slender. Paired gonites present, usually slender and elongate, flanking but basally separate from aedeagus.Aedeagus simple, with relatively elongate sclerotised basiphallus and short, membranous distiphallus. Aedeagal apodeme short, usually posteriorly directed. Sperm pump reduced. Cerci separate, variable in shape and size, nearly always conspicuous.

Female postabdomen ( Figs 10–12 ): Without specialised elongate segments; sternites 6, 7 and 8 all separate, 6 and 7 being large; spiracles of segments 6 and 7 present in pleural membrane. Cerci separate, short, slightly to noticeably longer than tergite 8, somewhat rounded, inconspicuous. Spermathecae 2, each with separate duct from oviduct; duct expanded distally; vesicle with darkly pigmented, relatively smooth, cuticular lining.

Discussion:There appear to be two species groupings in Natalimyza . In the first grouping of usually pallid species, the head and eye are depressed and the proboscis is somewhat reduced in size. In these species the bristles on the dorsal part of the head are usually reduced in length and strength. In the second grouping (to which N. milleri belongs) the head and eye are more or less rounded in profile and the proboscis is well developed. In these species the bristles on the dorsal part of the head are elongate and well developed. This said, however, there are intermediate forms, and no generic distinction is warranted at this stage. There is also significant intrageneric variation in the positioning of the r–m and m–cu crossveins, which are very closely approximated in some species, ranging to relatively well separated in others.

We decided not to dissect the male abdomen in order to investigate internal structures such as the testes and accessory glands. We consider that a substantial number of species need to be dissected to properly assess the development and form of these structures. Such studies are certainly indicated in future and may help elucidate phylogenetic relationships.

Figures

Figs 2–4. Natalimyza milleri: (2, 3) head, showing detail of all vestiture: (2) profile, (3) dorsal view; (4) wing (names of wing cells italicised, b2 – second basal cell).

Figs 5, 6. Natalimyza milleri, male postabdomen: (5) protandrial sclerites, ventral view (detail of dorsal structures, including tergite 6, omitted); (6) protandrogram (vestiture omitted).

Figs 7–9. Natalimyza milleri, male terminalia: (7) dorsal view, including detail of all vestiture (left margin of perianal field omitted to reveal internal structures); (8) right lateral view, showing detail of epandrium, surstylus and cerci (arrows identify external structures); (9) oblique ventral view (detail of epandrium, cerci, surstyli and other dorsal structures omitted).

Figs 10–12. Natalimyza milleri, female postabdomen: (10, 11) segments five to eight and cerci: (10) dorsal view (hypoproct omitted), (11) profile, slightly oblique to show detail of apical structures, vestiture of sternites 5 and 6 omitted (epiproct concealed beneath tergite 8); (12) spermatheca and apical section of spermathecal duct.