Empis (Sphenempis) Saigusa 2022, subgen. nov.
Creators: name: Saigusa, Toyohei
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Empididae
Empis

description: Empis (Sphenempis) subgen. nov.
Type species: Empis (Sphenempis) bicoloriventris Saigusa sp. nov.
Etymology. The subgeneric name is from the Greek, sphenos (wedge) + Empis, based on the wedge-shaped wing with strongly obtuse axillary incision.
Diagnosis. A specialized monophyletic group of Empis with slender body and legs, cuneate wings with very obtuse axillary incision and narrow axillary lobe, no acrostichal setae, strong but short ventral setae (spines) on apical part of four posterior femora, and male terminalia with pair of palm-shaped surstylus-like process from the bacilliform sclerites.
Description. Male. Head (Fig. 2A) spherical, slightly higher than long, occipital area somewhat swollen. Ocellar tubercle prominent, with pair of long setae. Occiput with postocular row of setae almost ending ventrally at middle of occiput with setae longer on vertex; short row of occipital setae at middle; a few fine short setulae near oral margin. Compound eyes almost continuous on dorsal half of frons, hardly separated from each other by diameter of upper facet, with facets almost same in size or slightly larger on upper part. Frons gradually and slightly widened towards antennal sockets on ventral half, bearing row of minute setulae. Face short, narrow, 1/2 as long as frons, 1/5 as wide as head, without setae. Antenna (Fig. 2B) inserted slightly below middle of anterior margin of head in lateral aspect, long, slender, slightly shorter than head; scape cylindrical, twice as long as thick, with subapical circlet of setulae; pedicel subspherical, narrowed basally, with circlet of setulae; postpedicel (3rd antennal segment) elongate, 1.7 times as long as combined length of basal segments, 4.5 times as long as subbasal thickness, slender, slightly thicker on basal 1/4, tapered to apex, with short (1/4 as long as postpedicel), fine stylus. Proboscis long, slender; labrum (Figs 2A, F) slender, 1.2–1.4 times as long as head height; prementum (Figs 2C, D) elongate, slender, 0.8 times as long as labrum, 8 times as long as wide, with short setulae mostly on lateral margins; labellum (Fig. 2E) pad-like but rather narrow, 3 times as long as wide in lateral aspect, slightly longer than 1/3 length of prementum and 1/3 as long as labrum, with several moderately long setulae, with shorter ones at tip of pseudotracheal branches; pseudotrachea without posterior trunk, anterior trunk obliquely emitting ca 20 simple branches. Palpus (Fig. 2G) small, short cylindrical, 1/4 as long as head, with longish apical setula and several shorter setulae.
Thorax extensively densely pollinose. Most of thoracic setae black, some setae pale; proepisternal and laterotergal setae black or white. Antepronotum with 1–3 pairs of setae; postpronotum with 1 seta and a few setulae; proepisternum with a few fine setulae, prosternum bare; 1–2 intrahumeral, 1–2 notopleurals, 0–1 supra-alar, 1 postalar, these setae often accompanying a few fine setulae; no acrostichals, several uniserial dorsocentrals; 1 (rarely 2) pair of scutellars; laterotergal brush of several (ca 10) setae. Legs: femora, tibiae and tarsi long, very slender, mostly short setose; mid and hind femora with several anteroventral, sometimes posteroventral short spines towards tip; hind tibia with a few dorsal setae longer than thickness of tibia; tarsi as thick as tibia or slightly slenderer, sparsely short setose and setulose; hind metatarsus not swollen.
Wing (Figs 3 A-C) narrow. Axillary incision very obtuse, about 130°, alula undeveloped, axillary lobe weakly developed, very narrow; discal cell rather short, about half as long as vein M 1 or slightly shorter, apically more or less acute, crossvein m-m nearly as long as middle section of M 4; angle of fork of veins R 4 and R 5 about 60–80°, former as long as or slightly shorter than half length of latter; R 5 almost parallel with vein M 1; all veins from discal cell strong to wing margin; vein CuA+CuP (so-called anal vein) strong and ending at wing margin, but slightly weaker towards margin; cell cua very narrow. Halter black, or white or darkened on apical part of knob; shaft of halter moderately long.
Abdomen slender, polished, short setose; abdominal tergum 1 thinly pollinose, sternum 1 bare; all terga and sterna simple, without deformations; abdominal segment 8 nearly half as long as segment 7.
Male terminalia: Cercus small, rectangular, simple, weakly sclerotized, projecting dorsally, pilose and bearing many longish setae on dorsal margin; epandrial lamella rectangular with short finger-like process at dorsodistal corner; palm-shaped surstylus-like process arising from apex of bacilliform sclerite, basal margin close to but separated from dorsal margin of epandrial lamella by narrow membranous slit; basiphallic sclerite (= transgonocoxal bridge of lower Brachycera) moderately large and flat; hypandrium slender, U-shaped, neither divided ventromedially nor produced posteriorly; phallus moderately long and slender, tapering apically, evenly, weakly curved.
Female (Fig. 1C). Similar to male. Frons wider, as wide as ocellar tubercle. Abdomen tapered to tip with slender cerci nearly as long as abdominal segment 8.
Included species. Empis (Sphenempis) amurensis Shamshev, 1998 from Amur region, E. (Sphenempis) bicoloriventris Saigusa sp. nov. from the Ryukyus and E. (Sphenempis) oshimai Saigusa sp. nov. from southern Kyushu.
Distribution. Sphenempis subgen. nov. is currently known from the Russian Far East and Japan (Kyushu and Ryukyus) and also collected in Honshu (Japan) and Thailand (C. Daugeron, pers. comm.). It is also likely to be found at least in Taiwan, as E. (Sphenempis) bicoloriventris sp. nov. occurs in the southernmost islands of the Ryukyus close to Taiwan. The subgenus will also likely be found in temperate regions of China.
Remarks. Sphenempis subgen. nov. shares the obtuse axillary incision of wing with Lissempis. However, the main resemblance between them is confined only to this character state, and they are abundantly different from each other. The proximally narrowed, cuneiform wing in the Empididae is widely found in weak flyers, and undoubtedly has evolved independently many times in different lineages of the family.
Differences from the type species of Lissempis: Sphenempis subgen. nov. differs from the type species of Lissempis, Empis nigritarsis Meigen (Fig. 3D) from Europe, in the following characters, most of which are treated as important in the subgeneric classification of the genus Empis: 1) the labrum is longer than head height (shorter in E. nigritarsis); 2) maxillary palpus is short cylindrical (moderately long and cylindrical in E. nigritarsis); 3) acrostichal setae absent (present in E. nigritarsis); 4) vein CuA+CuP fairly strong (much weakened on apical 1/2 except for extreme tip in E. nigritarsis (Fig. 3D)); 5) legs with several strong anteroventral and posteroventral spines on femora (only short setose in E. nigritarsis); 6) male terminalia with pair of well-developed palm-like processes arising from the bacilliform sclerite and small simple cercus (surstylus-like sclerite absent and cercus fairly well developed in E. nigritarsis); 7) hypandrium reduced to a slender, U-shaped sclerite (large, triangular sclerite projecting ventrodistally in E. nigritarsis). The apomorphic resemblance between E. nigritarsis and Sphenempis is found only in the cuneate wing shape. Thus, the above-mentioned differences indicate that E. nigritarsis and the subgenus Sphenempis cannot be included in a monophyletic subgenus in the genus Empis.
Differences from other species of Lissempis: In addition to E. nigritarsis, several species mostly from the Mediterranean district are assigned to the subgenus Lissempis (Chvála 2002; Shamshev & Kustov 2013; Kazerani et al. 2014). These species are different from the type species, nigritarsis, in some characters, viz. above-mentioned character 7, but they distinctly differ from Sphenempis in the above characters 3, 4, 5 and 6. Empis (Lissempis) curvitibia Chvála, 2002 lacks acrostichal setae, but the reduction of these setae is quite different from that of Sphenempis. In E. curvitibia, the absence of acrostichal setae is a result of the extensive loss of mesoscutal setae including not only the acrostichals but also dorsocentral setae, and only fine hairs are present around the postpronotum and notopleural area in the mesoscutum. The absence of acrostichals in Sphenempis was attained independently from other scutal setae including well-developed dorsocentral setae. Based on this evidence, the absence of acrostichals in Sphenempis has undoubtedly evolved independently from that in E. curvitibia.
The monophyly of the subgenus Sphenempis: The monophyly is supported by the combination of the following apomorphies: absence of acrostichals, abbreviated maxillary palpus, cuneate wing, palm-like process in the male genitalia, spine-like ventral setae on the femora, and slender body. The complete vein CuA+CuP is one of the plesiomorphic characters discriminating Sphenempis from Lissempis.
Empis species resembling Sphenempis: In addition to Lissempis, there are at least two monophyletic groups of Empis resembling Sphenempis subgen. nov. on the basis of the obtuse axillary incision of the wings and the absence of acrostichal setae. One group consists of species from Japan and North America (e.g., Empis kasparyani Shamshev (Fig. 3E) from Kuril Islands, Empis latrappensis Ouellet from eastern North America) and of unnamed species from China, Amur and Taiwan. The other group consists of species from the Nearctic Region (Empis leptogastra Loew (Fig. 3F) and its allies). These groups have basally cuneate wings and ventrally spinose mid and hind femora as in Sphenempis subgen. nov., but are considerably different from the latter in several other diagnostic characters. The first group is more closely related to Sphenempis subgen. nov. and may be included in it by future works based on more extensive phylogenetic analysis researching together with the subgenus Anacrostichus Bezzi, that has ventrally spinous femora but no acrostichal setae in some of its included species.
Key to males of species of the subgenus Sphenempis
1 Abdomen almost uniformly polished blackish brown (Figs 1D, E); halter and laterotergal setae black.................. 2
- Abdomen bicolored, yellowish white on anterior half and blackish brown on posterior half (Figs 1A, B); halter white, often darkened on apical half of knob; laterotergal setae pale................................... E. bicoloriventris sp. nov.
2 Hind femur long and slender, slightly more than 12 times as long as thick (Fig. 6A); mid and hind femora with weak anterior preapical bristle (Figs 6E, F); mesoscutum dark greyish brown pollinose when viewed from above; axillary lobe of wing wider, widest before middle (Fig. 3C); distal process of palm-like process of genitalia shorter, slightly longer than wide (Figs 6H, I).................................................................................... E. oshimai sp. nov.
- Hind femur shorter and thicker, 10 times as long as thick (Fig. 5A); mid and hind femora with strong anterior preapical bristle (Figs 5E, F); mesoscutum deep blackish brown pollinose when viewed from above; axillary lobe of wing narrower, widest at middle (Fig. 3B); distal process of palm-like process of genitalia longer, almost three times as long as wide (Figs 5H, I)..................................................................................... E. amurensis Shamshev
description: Published as part of Saigusa, Toyohei, 2022, Sphenempis, a new Empis subgenus (Diptera, Empididae) from the Eastern Palaearctic Region, pp. 105-117 in Zootaxa 5129 (1) on pages 106-108, DOI: 10.11646/zootaxa.5129.1.6, http://zenodo.org/record/6488262