Dexia Meigen, 1826

Zhang, Chun-Tian, Shima, Hiroshi & Chen, Xiao-Lin, 2010, A review of the genus Dexia Meigen in the Palearctic and Oriental Regions (Diptera: Tachinidae) 2705, Zootaxa 2705, pp. 1-81 : 5-8

Genus Dexia Meigen, 1826

Dexia Meigen, 1826: 33 . Type species: Musca rustica Fabricius, 1775: 777 , by designation under Plenary Powers of ICZN, 1988: 74 [Palearctic]. — Robineau-Desvoidy 1830: 311. — Macquart 1834: 190, 1835: 211. — Zetterstedt 1859: 6173. — Robineau-Desvoidy 1863b: 384. — Brauer & Bergenstamm 1889: 120 (key), 1893: 174. — Wulp 1896: 138. — Pandellé 1896: 152. — Coquillett 1910: 532 (type species of Dexia and Dexilla ). — Stein 1924: 237. — Lundbeck 1927: 268. — Curran 1927: 103 (key and descriptions). — Townsend 1936: 11, 274 (diagnosis of Dexiini , including Dexia ). — Emden 1954: 30 (key). — Herting 1960: 125 (biology). — Zimin et al. [1969] 1988: 1273 (key). — Kolomiets 1970: 53 (redescription). — Crosskey 1976: 45, 177 ( Dexia of usage and catalog). — Crosskey 1977: 601 (catalog). — Mesnil 1980: 38 (Palearctic Dexia , with Dexilla in synonymy). — Dear & Crosskey 1982: 115 (key). — Richter & Farinets 1983: 813 (key to larvae). — Herting 1984: 143 (catalog). — Crosskey et al. 1986: 282 (proposed type species designation for Dexia ). — Shima 1989: 869 (list). — Chao & Liang 1992: 805 (key). — Herting & Dely-Draskovits 1993: 365 (catalog). — Tschorsnig & Herting 1994: 14, 80, 156 (key and notes). — Chao et al. 1998: 2154 (notes). — Ziegler & Shima 1996: 429 (checklist). — Tschorsnig & Richter 1998: 737 (Palearctic key). — Ziegler 1998: 29, 101, 164−165, 185 (larvae and puparia). — Sabrosky 1999: 109 (familygroup names). — Richter 2004: 355 (key). — Zhang & Shima 2004: 49 (Chinese Dexia ). — Zhang et al. 2004: 127 (checklist). — Zhang et al. 2005: 304 (list). — O’Hara et al. 2009: 28 (catalog). — Chao et al. 2009: 575 (fauna).

Dexilla Westwood, 1840: 140 . Type species: Musca rustica Fabricius, 1775 , by original designation. — Townsend 1938: 276 (redescription). — Crosskey 1967: 107.

Ida Robineau –Desvoidy, 1863b: 389. Type species: Ida petiolata Robineau-Desvoidy, 1863 (= Musca rustica Fabricius, 1775 ), by monotypy. Preoccupied by Jay 1836. — Bezzi & Stein 1907: 445 (as syn. of Dexia ). — Herting 1974: 40 (as syn. of Dexia ). — Mesnil 1980: 38. — Evenhuis et al. 2010: 93.

Phasiodexia Townsend, 1925: 250 . Type species: Plasiodexia flavida Townsend, 1925 , by original designation. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 178 (as syn. of Dexia ). — Mesnil 1980: 39 (as subgenus of Dexia ).

Sumatrodexia Townsend, 1926a: 26 . Type species: Sumatrodexia brevirostris Townsend, 1926 (= Dexia extendens Walker, 1856 ), by original designation. — Baranov 1932: 213. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 177 (as syn. of Dexia ). — Mesnil 1980: 39 (as subgenus of Dexia ).

Calotheresia Townsend, 1926a: 29 . Type species: Calotheresia sumatrensis Townsend, 1926 (= Dexia fulvifera Röder, 1893 ), by original designation. — Baranov 1932: 213. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 178 (as syn. of Dexia ). — Mesnil 1980: 39 (as subgenus of Dexia ).

Eomyoceropsis Townsend, 1926a: 29 . Type species: Eomyoceropsis longipennis Townsend, 1926 , by original designation. — Baranov 1932: 213. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 178 (as syn. of Dexia ).

Eoptilodexia Townsend, 1926b: 535 . Type species: Eoptilodexia longipes Townsend, 1926 , by original designation. — Baranov 1932: 213. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 177 (as syn. of Dexia ). — Mesnil 1980: 39 (as subgenus of Dexia ).

Eomyocera Townsend, 1926b: 537 . Type species: Eomyocera carinata Townsend, 1926 , by original designation. — Baranov 1932: 213. — Malloch 1935: 581. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 177 (as syn. of Dexia ). — Mesnil 1980: 39 (as subgenus of Dexia ).

Asbellopsis Townsend, 1928: 378 . Type species: Asbellopsis luzonensis Townsend, 1928 , by original designation. — Crosskey 1976: 178 (as syn. of Dexia ).

Barydexia Townsend, 1928: 379 . Type species: Barydexia bivittata Townsend, 1928 , by original designation. — Baranov 1932: 213 — Crosskey 1976: 178 (as syn. of Dexia ).

Calotheresiopsis Baranov, 1932: 214. Type species: Calotheresiopsis orientalis Baranov, 1932 (= Dexia basifera Walker, 1859 ), by original designation. — Crosskey 1967: 96 (as syn. of Dexilla ). — Crosskey 1976: 178 (as syn. of Dexia ).

Dexillina Kolomiets, 1970: 57 (as subgenus of Dexia ). Type species: Musca vacua Fallén, 1817 , by original designation. — Crosskey 1976: 178.

Dexillosa Kolomiets, 1970: 57. Type species: Dexia (Dexillosa) amurensis Kolomiets, 1970 (= Dexia fulvifera Röder, 1893 ), by original designation. — Crosskey 1976: 178. — Mesnil 1980: 38.

Diagnosis. Facial carina usually developed; parafacial wide; gena broad, about as high as length of antennal pedicel and 1st flagellomere combined; eye bare; arista long plumose; proepisternum usually bare; second costal sector of wing hairy ventrally; legs elongate, mid tibia usually with 1 (male) or 2 (female) anterodorsal setae; abdomen usually broadly yellowish, abdominal syntergite 1+2 medially excavate to its hind margin; male terminalia with surstyli usually narrow and pointed apically or sometimes bluntly rounded at apex; pregonite short and bent posteriorly, distiphallus long plate-like, sclerotized basal part longer than membranous apical part.

Generic description. Head. Sexually dimorphic; frons usually less than 1/7 of head width in male, more than 1/3 of head width or eye width in female; parafacial bare, 1.5−3 times as wide as 1st flagellomere; facial carina developed, usually high, long and pointed on ridge; gena broad, higher than length of antenna or 1/3 eye height; lower margin of face slightly protruding forward. Inner vertical seta 0.3−0.4 times as long as eye height, outer vertical seta hair-like; ocellar seta strong; frontal setae descending at most to level of upper margin of pedicel; fronto-orbital plate at most with some short and fine hairs on inner portion; prevertical and orbital setae absent in male, 1 prevertical and 2 proclinate orbital setae present in female; vibrissa inserted above lower margin of face; upper occiput with several black hairs behind postocular setae. Antenna with 1st flagellomere 2−5 times as long as wide or at most as long as genal height; arista plumose, total width including plumosity 2−4 times as wide as 1st flagellomere. Prementum 2.5−6.0 times as long as wide. Palpus usually developed, slender, not inflated, rarely very small. Eye bare.

Thorax. Broadly brown-black in ground color, scutellum usually reddish yellow; scutum with reddish yellow to yellowish white pruinosity, four brownish longitudinal black vittae present on scutum, sometimes inner and outer vittae merged to form 2 broad vittae. Prosternum bare, usually twice as long as wide, in D. flavipes sometimes with 1−4 hairs; proepisternum usually bare, rarely haired; postpronotal lobe with 2−3 setae, if 3 then arranged in a straight line; 0−2 presutural and 1−2 postsutural acrostichal setae; 2−3 presutural and 3 (rarely 4) postsutural dorsocentral setae; 1−3 postsutural intra-alar setae; 2−3 postsutural supra-alar setae, 1st one distinctly shorter than notopleural seta; scutellum with 3 pairs of marginal and 1 pair of discal setae; 2 or 3 katepisternal setae; katepimeron bare or hairy. Anterior and posterior lappets of posterior thoracic spiracle unequal in size; posterior lappet larger and subcircular. Anatergite bare below lower calypter. Wing pale brownish hyaline, sometimes brown or dark tinged; lower calypter yellowish or milky white or brown, with short or long fringe on outer margin. Costagial seta undeveloped; costal spine present or absent; second costal sector always with fine hairs ventrally; basal node of vein R 4+5 with 2−3 hairs on dorsal and ventral surfaces; vein M at bend nearly right-angled, appendix short, at least as long as half of crossvein r-m; cell R 4+5 narrowly open. Lower calypter large, yellowish or white, bare on dorsal surface, with long or short fringe on outer margin. Legs long and slender, inner anterior surface of fore coxa bare or predominantly bare; fore tarsi distinctly longer than head height, tarsi and claws black, pulvilli yellowish, fore claws and pulvilli longer than or equal to tarsomere 5 in male, and shorter than tarsomere 5 in female; fore tibia with a row of short anterodorsal setae on basal 2/3 and 2 posterior setae; mid tibia usually with 1 (male) or 2 (female) anterodorsal setae, 2−3 posterodorsal and 1 ventral setae; hind tibia with 2−4 anterodorsal, 1−3 posterodorsal and 2−3 ventral setae, 2 preapical dorsal and 2 apical ventral setae.

Abdomen. Syntergite 1+2 always medially excavated to its posterior margin; tergites 3 to 5 of male usually with 1−2 pairs of median discal setae, females usually without them; tergite 3 usually with 2 median marginal setae, tergites 4 and 5 each with a row of marginal setae. Abdominal sternites concealed beneath margins of tergites. Male terminalia. V-shaped median cleft of sternite 5 deep and wide, posterior lobe blunt apically; cerci long and pointed at apex; surstylus slender, narrow and pointed apically or bluntly rounded at apex; pregonite short, slightly bent posteriorly; postgonite as long as or shorter than basiphallus; distiphallus long, flat and plate-like, with spinules on ventral membranous surface, membranous apical part shorter than sclerotized basal part.

Distribution. Dexia species are found in the Oriental, Palearctic and Afrotropical Regions of the Old World. Land distribution pattern: Dexia alticola , D. caldwelli , D. chaoi , D. chinensis , D. fraseri , D. maritima , D. rustica , D. tenuiforceps , D. vacua , D. ventralis and D. violovitshi are distributed in parts of Eurasia. Dexia flavida perhaps extended to islands from Asian mainland. Island distribution pattern: Dexia atripes , D. basifera , D. bivittata , D. fusiformis , D. hainanensis , D. kurahashii , D. lepida , D. longipes , D. longipennis , D luzonensis , D. major , D. montana , D. seticincta , D. subnuda , D. sumatrensis , D. velutina , D. vicina and D. vittata are only distributed on islands of China, Indonesia, Malaysia and Philippines. Dexia divergens , D. extendens , D. flavipes , D. gilva and D. monticola perhaps extended to Asian mainland from above islands. Wide Palearctic-Oriental distribution pattern: Dexia fulvifera is distributed from Sri Lanka to Japan, NE China and Russian Far East.

Remarks. It is usually difficult to define the genera of Dexiini on the basis of diagnostic characters and Dexia is not an exception. Dexia is distinguished from other similar genera by a combination of characters, as given in the diagnosis above. Most of these characters are usually found in other genera of Dexiini . One character state, the long basal sclerotized part in comparison with distal membraneous part of the distiphallus, appears to be a synapomorphy of Dexia , although it may occur in a few other genera of Dexiini as a homoplasy.

Dexia is most similar to Philippodexia Townsend in the Oriental Region in having a yellowish head with arista plumose, and abdominal syntergite 1+2 always medially excavated to its posterior margin; but the latter genus has a bare ventral second costal sector of the wing, pregonite long and bent posteriorly, and sclerotized basal part of distiphallus shorter than membranous apical part.