Megamerinidae Hendel 1913
Creators: name: Lonsdale, Owen
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Megamerinidae

description: Megamerinidae Hendel, 1913
(Figs 98–123, 403)
Type genus: Megamerina Rondani 1861: 10 [new name for Lissa Meigen 1826: 370, preoccupied by Leach (1815) (Decapoda)], by Hendel (1913: 90). Type species of genus: Ocyptera dolium Fabricius, 1805: 315, by automatic designation [type species for Lissa Meigen (Chliza loxocerina Fallén, 1820 = Ocyptera dolium) by monotypy].
Megamerinidae, as it is presently defined, is a small and morphologically conserved family mostly consisting of Texara species (at least 14 species) that are found mainly in the Oriental Region, but also in the Palaearctic. The remaining two monotypic genera are the Palaearctic Megamerina, and the Chinese (Hubei, Sichuan and Zheijang Provinces) Protexara Yang [not examined]. Present generic limits are heavily reliant on the development of the fronto-orbital seta, being either strong (Texara), weak (Protexara) or absent (Megamerina). Protexara is further characterized by several small spines on the fore and mid femora, and the male cercus and surstylus are broadest basally (Yang, 1996), but the male terminalia are otherwise reminiscent of Megamerina (Figs 106–109) and may prove to belong in that genus. The phallus of Texara is distinct (Figs 116–117), including one pair of terminal corkscrew-like filaments.
The Megamerinidae was last treated by McAlpine (1997a), who discussed the history and relationships of the family, Krivosheina et al. (1996), who provided a key to Russian species, and Yang (1996), who treated the Chinese fauna. Xue and Chao (1998) treated the Megamerinidae of China, describing five new species. Steyskal (1977e) provided a catalogue for Oriental species, and Nartshuk (1984) provided one for Palaearctic species.
Hennig’s (1965) concept of Megamerinidae also included the monotypic Palaeotanypeza Meunier from Baltic amber (upper Eocene?), which was originally described as Tanypezidae (Meunier, 1917). The genus was only ten- tatively maintained as Megamerinidae by D.K. McAlpine (1997a) and J.F. McAlpine (1989), but examination of both sexes for the present study strongly support placement in Megamerinidae. It is clearly distinct from the more slender living taxa, however, whose mostly narrowed legs, longer petiolate abdomen and smaller head with elongate antenna exaggerate the thicker portions of the body, including the hind femur. Dimensions of the fossil taxon (see Hoffeins & Tschirnhaus (2009: figs 7–9)) are closer to other generalized acalyptrates in some respects, although the hind femur is about as thick as that of modern megamerinids. J.F. McAlpine (1989) suggested separate subfamilial rank for the genus, and while possibly justified, seems unnecessary.
Biology. Larvae of Palaearctic Texara and Megamerina have been found to be predaceous on other fly larvae under the bark of fallen deciduous trees (willow, poplar, oak and especially aspen) and in decaying vegetation (Krivosheina & Krivosheina, 1997), agreeing with Hennig’s (1943) earlier assumptions. Adult specimens have been collected in damp meadows, various mixed and deciduous forests, undergrowth, and on rotting wood and cut aspen (Roháček, 2016).
Immature stages. Descriptions and illustrations of the third instar larva and puparium of M. dolium (Fabricius) were provided by Krivosheina & Mamaev (1967) and Hennig (1943), respectively. Ferrar (1989) summarized knowledge on larvae and puparia known at the time. Krivosheina & Krivosheina (1997) redescribed the larva of M. dolium, described the larva of T. savolaineni (Frey), and described the larva and puparium of T. stackelbergi Krivosheina, Krivosheina & Nartschuk.
Adult Diagnosis (extant genera). Relatively large, long, slender and heavily-built (Figs 98–105). Body length usually 8.0–18.0mm. Colour black with antenna, face, halter and most of legs white to yellow; setae black to white, setulae white; wings slightly infumated. Antenna porrect; pedicel without dorsal seam; arista short-plumose. Head subspherical in profile; face narrowed into thin medial carina; frons projecting and tapering anteriorly with one pair of oblique lateromedial folds; frons with one pair of dark velvety lateromedial patches and single silvery patch behind ocelli. Vibrissa, postocellar, and sometimes ocellar seta absent. Postpronotal absent. Enlarged hind femur with two rows of spines ventrally; hind tibia curved and with double sclerotized ridge on venter fused along most of length; all femora with row of glands both posteroventrally and anteroventrally (only posteroventral on fore and mid femora in Syringogastridae). Fronto-orbital seta present or absent. Precoxal bridge absent; postmetacoxal bridge present; thorax produced at narrow point of attachment to abdomen. Costa unbroken; sc complete (Fig. 403).
Adult Definition (extant genera). Relatively large and slender, heavily-built and well sclerotized (Figs 98– 105). Body length usually 8.0–18.0mm. Colour black with antenna, face, halter and most of legs white to yellow; setae black (major setae) to white, setulae yellowish-white. Scutum minutely punctate at base of setulae.
Chaetotaxy: 1 inner vertical; 1 outer vertical; 0 (Megamerina) or 1 weak (Protexara) or well-developed (Texara) fronto-orbital; 0 ocellar; 0 postocellar; vibrissa absent. 0 presutural intra-alar; 0 postpronotal; 1 posterior notopleural; 2 posterior supra-alar; 0 posterior intra-alar; 0–1 dorsocentrals; 0 acrostichals; 1 apical scutellar (lateral seta absent); 0 proepisternal; 0 anepisternal; 0 katepisternal. Pedicel with dense dark setulae. Frons with irregular lateral row of proclinate to lateroclinate setulae; face, parafacial, gena with dense white pubescence forming narrow band around eye to dorsum of occiput; sparse hairs on face continuing as shorter series of denser hairs on venter of gena; frons with one pair of brownish-purple lateromedial velvety patches. Occiput and back of head with long white (often weak and curled) to black (straighter) pile that are not differentiated into separate postoccular setae. Thorax and legs with dense to sparse white setulae, except on postalar wall (microtomentose) metanotum (microtomentose to partially bare on anatergite and posterior half of katatergite) and pleuron behind wing base and below postpronotum; proepisternum otherwise with patch of short, dense, isolated (usually white) hairs that extends onto anterolateral surface of fore coxa; notal setulae with pattern of “partings”, most noticeably between dorsocentral rows, with setulae directed inwards along a single line postsuturally, and along two parallel lines presuturally (Fig. 98). Fore tibia with white setulae dense (Fig. 99). Mid tibia with ventroapical seta. Pregenitalic abdominal tergites with longer setae laterally, especially along posterior margin of T1, and sometimes to a lesser degree along posterior margins of other pregenitalic tergites; posterior setae on S1 also longer.
Head. Antenna porrect, pedicel without dorsal seam, sometimes inner-distal margin slightly angulate; first flagellomere discoid with apical margin sometimes slightly truncated; arista white, short plumose to pubescent. Anterior margin of frons with two medial folds extending back from ptilinal suture (i.e. ptilinal suture H-shaped) that raises medial section of frons (“medial frontal lobe” of McAlpine (1997a)); produced anteriorly (conspicuous when viewed laterally) with sides broadly rounded to cover dorsolateral margins of face and parafacial (Figs 101–102). Lunule present, medially grooved, horizontal with anterior section curved down between antennal bases (Fig. 100). Sides of face converging medially, enclosing centre of face within carinate sulcus (continuous with groove on lunule); sulcus split ventrally at epistoma (usually narrow, but wider than high in Megamerina). Clypeus rounded, anterior section subrectangular and sometimes shallowly notched. Back of head broadly rounded, vertex slightly shifted forward; with pronounced microsetulose lobe above foramen and teardrop-shaped silvery tomentose patch reaching ocellar tubercle.
Thorax. Proepisternum shifted dorsally, fused to posteriorly displaced postpronotum. Transverse suture vestigial medially, at midpoint of scutum; supra-alar carina shallow; postalar wall sharply angled downwards with margin slightly carinate. Scutellum and subscutellum small, shallow. Greater ampulla present. Katepisternum and meron fused (suture evident as minute pit over mid coxa); anepisternum deeply receding below postpronotum. Coxopleural streak present. Metathorax with cylindrical extension meeting abdomen; sharply and deeply recessed above spiracle. Metasternum extending between hind coxae as pointed process, not reaching postmetacoxal bridge. Precoxal bridge absent; prosternum arrowhead-shaped; presternum small, spindle-shaped, duplicated; subcervical sclerite floating, linear; postmetacoxal bridge present, high; membrane around prosternum and hind coxae slightly sclerotized, scaled.
Wing. (Fig. 403) M 4 and CuA+CuP reaching wing margin. Cell br bulging into dm. Cell cu a short and CuA straight. Anal cell and most of cell bm bare. Veins R 4+5 and M 1 subparallel, slightly converging apically. Costa unbroken; sc complete, ending far from apex of R 1. Calypter hairs moderately long.
Legs. Hind femur strongly swollen (Figs 98–99) with two rows of spines (usually 12–14) ventrally; hind tibia curved (curve corresponding to shape of swollen femur) and with one pair of sclerotized ridges ventrally that may be fused along most of length. Fore and mid femora also slightly swollen medially, but not nearly as extensively as hind femur; with 3–4 small ventral spines in Protexara. All femora with row of glands both posteroventrally and anteroventrally (Fig. 103) with surrounding pigment orange. Tarsomeres with strong ventroapical setae; fore and mid basitarsomeres with long ventral hairs.
Abdomen. T1 and S1 broadly emarginated anteriorly to provide membranous space that folds to meet thorax when abdomen angled (Fig. 119). Segments longer than wide. Sternites 1–5 weakly sclerotized marginally; S1 with dark, transverse posteromedial sclerotization; S2 with one pair of internal, anterolateral hooks. Spiracles 1–6 in membrane. At least T2 (sometimes also T3 and T4) with pair of silvery posterolateral patches (Fig. 99).
Male genitalia. (Figs 106–117) Right spiracle 7 present, in membrane. Tergite 6 divided into two, small, narrow dorsal strips. S7 separate or partially fused to right anterolateral margin of S8. S6 bare, narrow, adjacent to S7. S8 large, elongate, tapering apically. Epandrium tapering basally and with thickly sclerotized distal margin. Cercus subtriangular, usually widest apically, with pointed tubercle-like setae on inner surface. Surstylus movable, strongly incurved, with inner patches of basal and apical tubercles. Subepandrial sclerite V-shaped with two ventral setae on each side. Hypandrium elongate, arms meeting posterodorsally; distally fused to short anteroventral extensions of phallapodeme that continue slightly distal of hypandrial margin; distal half of hypandrium weakly sclerotized excluding narrow margin, thin texturing and one pair of floating, setose sclerites. Pregonite apically spinulose and with comb of short, stout setae, directed anteriorly, perpendicular to postgonite. Postgonite dark, rod or ribbon-like, confluent with base of pregonite and extending to phallapodeme. Basiphallus small, fused to distiphallus. Epiphallus sometimes present. Distiphallus with long, straight base composed of two parallel ribbons that bend ventrally at apex; apically with thick spinulose process on right side (“scabrous process” of McAlpine (1997a)), and with dark sclerite(s) and filamentous processes (“terminal filaments” of McAlpine (1997a)) on left side; some filaments modified into double corkscrew in Texara (Figs 116–117). Ejaculatory apodeme with large, stout stem ending in short, clear blade with supporting ribs; stem and blade rotated 90° relative to insertion of duct; stem with stout medial carina above duct; sperm pump with paired marginal sclerotized bands.
Female genitalia. (Figs 118–123) T6 and S6 widest before midpoint, closely associated but not fused. T7 and S7 fused into long, thin tube enclosing spiracles. T8 and S8 weakly sclerotized, separate, and with numerous longitudinal grooves. T10 and S10 small, narrow and minutely grooved; T10 with lateral fold. Cercus length more than twice width, slightly incurved, broadly rounded apically. Membrane between segments 5–8 long, and segments past segment 5 long and thin, allowing for most of these to telescope. Spermatheca slightly elongate with pointed apex, surface sparsely covered with minute divots; spermatheca and apex of duct pigmented.
Variation—Paleotanypeza (fossil). (Tschirnhaus & Hoffeins, 2009: figs 7–9) As described above, except as follows. Body length approximately 8.8–9.5mm; one female (with elongate ovipositor extended) 18.0mm long. Single well-developed fronto-orbital present; one dorsocentral seta (slightly shorter than scutellar seta); small lateral hairs on face slightly shorter, but present; cannot verify if frons with lateral velvety patches; silvery tomentose patch behind ocelli not present; “partings” of setulae not evident on notum. First flagellomere subcircular; pedicel length less than half height, with angulate projection modestly developed on inner surface and shallowly developed on outer surface; arista bare; cannot verify presence of medial groove on lunule; face not sunken laterally beside parafacial; clypeus not notched anteromedially; without microsetulose lobe above foramen; back of head “normally” rounded. Thorax without proepisternum shifted dorsally; postalar wall not sharply angled or carinate; katepisternum and meron not fused; typically acalyptrate in dimensions, without severely narrowed or recessed regions. Swollen hind femur not as evident as all legs are well-developed, not narrowed; fore femur with ventrodistal rows of spines as on hind leg, two anterior and three posterior spines on male and 5 anterior and 7 posterior spines (1 and 3 shorter) on female; hind tibia not curved, without sclerotized ridges; hind tibia with ventroapical seta towards anterior surface; male hind tibia with row of black setulae on ventrobasal half. Abdomen thicker at base, not elongate or narrowed; cannot verify position or presence of spiracles; silvery regions on abdomen restricted to tergite 1 (patches broad, posterolateral, narrowly connecting) and tergite 4 (broad lateral stripe). Female segments 6–10 extremely elongate with extensive intersegmental space; T6 and S6 well-developed, segments 7–10 indistinctly sclerotized. Male tergite 6 not visible, but similarly small if present; cercus broad and bilobed apically, with additional floating mediobasal sclerotized patch; surstylus apically broad with margin straight, distomarginal tubercles densely arranged in comb-like line (reminder of tubercles on inner face not visible if present).
description: Published as part of Lonsdale, Owen, 2020, Family groups of Diopsoidea and Nerioidea (Diptera: Schizophora) - Definition, history and relationships, pp. 1-177 in Zootaxa 4735 (1) on pages 22-24, DOI: 10.11646/zootaxa.4735.1.1, http://zenodo.org/record/3670762