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

description: Empis (Sphenempis) bicoloriventris sp. nov.
(Figs 1A–C, 2, 3A, 4)
Type material. HOLOTYPE ♂, labelled: [Mt. Nago-dake] alt. 50-150 m / 26.35N 127.59E /Nago. Okinawahontô / Japan / 2nd March 2008 / H. Nakayama leg.; [HOLOTYPE]/ Empis (Sphenempis) / bicoloriventris / Saigusa, 2022 (in Kyushu University Museum). PARATYPES: 1♂, [OKINAWA]/ Yona/ Okinawa-jima/ Dec. 6, 2006 / T. SAIGUSA leg.; 2♂ 1♀, RYUKYUS /OKINAWA- / HONTO, Kudeken/ 20.III.1954 / Syusiro Ito, Japan-U.S./ Co-op. Sci. / Programme; 3♀, [OKINAWA-jima]/ Tanagawagumui/ Anba, Kunigami/ March 3, 1997 / T. SAIGUSA col.; 1♀, [OKINAWA-jima]/ Ryukyu Univ. Exp./ Forest Yona/ March 3, 1997 / T. SAIGUSA col.; 1♀, same data, March 5, 1997; 1♂, Ishigaki-jima/ Banna-dake (foot)/ 18.III.2002 /M. SUGIMOTO col.; 1♀, [OKINAWA] /Omotodake/ Ishigakijima / March 25, 2004 / T. Nakamura col.; 5♂, [ISHIGAKI-JIMA]/ small torrent south of Golf field/ 95m, Hirae-Ômata/ January 29, 2019 / T. SAIGUSA col.; 3♀, [ISHIGAKI-JIMA]/ North of Golf field/ 100m, Hirae- Ômata / January 28, 2019 / T. SAIGUSA col.; 2♂, I-19-1953 / Ryukyu Is./ T. SHIRAKI, Iriomote Is./ Ohara.
Etymology. The specific name bicoloriventris is based on the bicolored male abdomen, white basally and blackish brown distally.
Diagnosis. Mesonotum densely light brownish pollinose; laterotergal brush of whitish setae; male abdomen whitish on anterior half, blackish brown on posterior half; halter pale.
Description. Male (Figs 1A, B). Body length 3.3–4.1 mm; wing length 3.6–3.8 mm. Coloration. Head blackish brown, densely light grey pollinose. Antenna with pedicel and scape brown, postpedicel black with extreme base brown. Palpus pale brown; labrum yellow, dark brown at extreme tip; labium pale brown, with pale yellowishbrown labella. Thorax blackish brown, densely light grey pollinose, postpronotum polished brown on lateral part; viewed from above pollinosity of mesoscutum more brownish on area surrounding posterior part of dorsocentrals; prescutellar area and scutellum ash grey pollinose. Abdomen bicolored, anterior 4 segments yellowish white, thinly white pollinose, clothed with short white setae, posterior 4 segments and genitalia polished blackish brown, with darker setae. Wing uniformly infuscate to light brown, with membrane somewhat polished, pterostigma indistinct; veins dark brown; squama whitish with pale fine setae. Halter yellowish white, apical half of knob dark in specimens from Okinawa-jima, entirely white in specimens from Ishigaki-jima and Iriomote-jima. Legs yellow; coxae thinly light grey pollinose; mid and hind coxae somewhat infuscate; trochanters black apically; femora and tibiae polished yellow, somewhat darkened on apical 1/2; tarsi brown.
Most structural and chaetotaxy characters as in subgenus description. Wing (Fig. 3A) about 3.5 times as long as wide: cell r 2+3 almost as wide as cell r 4+5 at level of tip of vein R 2+3; discal cell half as long as vein M 1; axillary lobe narrow, widest at middle, with evenly curved margin. Legs (Figs 4A–F): Mid femur with 3–4 anteroventral and 1–2 posteroventral spines, hind femur 12.5 times as long as thick, with 3–4 anteroventral spines, without posteroventral spines. Terminalia (Figs 4G–I): Palm-like process with two moderately long finger-like lobes and short proximal lobe; cercus not raised posteriorly.
Female (Fig. 1C). Similar to male. Body length 3.7–4.1 mm; wing length 3.6–4.5 mm. Frons almost as wide as ocellar tubercle (distance between posterior ocelli); mesoscutum more brownish pollinose, particularly along dorsocentral setae; wings clear, not infuscate; abdomen with polished brown terga and yellowish brown sterna, sparsely clothed with short brown setae; cercus slender, as long as abdominal segment 8.
Distribution. Ryukyus (Okinawa-jima, Ishigaki-jima, Iriomote-jima), Japan.
Type locality. Mt. Nago-dake (26.35N 127.59E), Okinawa-jima, Ryukyus, Japan.
Remarks. The male of this species is easily distinguished from E. amurensis by the pale (almost white in fresh material) anterior half of the abdomen. The female also may be distinguished from unknown females of the following two species by the basally white halter. This species is not rare in the Ryukyus. The color difference in halteres between the males from Okinawa-jima and the Yaeyama islands (Ishigaki-jima, Iriomote-jima) is found, but there are no differences in the male genitalia between these two populations. This species appears from January to March.
The white colored male abdomen is similar to that of the western North American species, Empis melanderi Arnaud & Birchim (Arnaud & Birchim 1966, fig. 1). This species lacks acrostichals as in Sphenempis, but differs from the latter in the wing shape, apically weakened vein CuA+CuP, simple mid and hind femora without strong spine-like setae and the male terminalia with well-developed cerci and no palm-like sclerites.
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 108-111, DOI: 10.11646/zootaxa.5129.1.6, http://zenodo.org/record/6488262