Dexia vacua ( Fallén, 1817 )

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 : 68-70

Dexia vacua ( Fallén, 1817)

Figs. 85−88

Musca vacua Fallén, 1817: 240 .

Dexia cincta Robineau-Desvoidy, 1830: 312 . — Herting 1974: 40 (as syn. of D. vacua ).

Dexia gracilis Robineau-Desvoidy, 1830: 313 . — Robineau-Desvoidy 1863b: 389. — Herting 1974: 40 (as syn. of D. vacua ).

Dexia aurinia Walker, 1849: 847 . — Austen 1907: 343 (as syn. of D. vacua ). — Crosskey 1974: 292, 305 (type material, junior syn. of D. vacua ).

Dexia vacua: Macquart, 1835: 212 . — Zetterstedt 1844: 1265, 1859: 6173. — Rondani 1862: 76. — Robineau- Desvoidy 1863b: 388. — Pandellé 1896: 160. — Bezzi & Stein 1907: 446. — Stein 1924: 238. — Lundbeck 1927: 270. — Emden 1954: 30. — Sabrosky & Arnaud 1965: 982 (catalog). — Kolomiets 1970: 61, 67 (key and redescription). — Mesnil 1980: 47 (redescription) — Herting 1984: 144 (catalog). — Richter & Farinets 1983: 816 (1st instar larva). — Chao & Liang 1992: 806 (key), misidentification. — Herting & Dely-Draskovits 1993: 366 (catalog). — Tschorsnig & Herting 1994: 81, 157. — Chao et al. 1998: 2154, misidentification. — Richter 2004: 355 (key). — Shi 2004: 90 (misidentification). — Chao et al. 2009: 576 (fauna), misidentification.

Diagnosis. Prementum 2.5−3 times as long as wide; 3 presutural and 3 postsutural dorsocentral setae; 2 katepisternal setae; tegula and legs reddish yellow; abdomen reddish yellow, entirely with grayish white pruinosity; syntergite 1+2 without median marginal setae.

Description. Mesnil (1980) redescribed this species in detail. Here we give some additional measurements and diagnostic characters.

Body length. 7.5−9.8 mm.

Male. Head with grayish white pruinosity. Frons about 0.14 times as wide as head width; parafacial about twice as wide as 1st flagellomere; facial carina weakly developed, low and pointed on ridge; gena about 0.4 times as wide as eye height; ocellar seta as strong as upper frontal setae; fine inner vertical seta 0.25−0.36 times as long as eye height, slightly shorter than ocellar seta; 1st flagellomere 2−3.5 times as long as pedicel; total width of arista including plumosity 2−4 times as wide as 1st flagellomere; prementum 2.5−3 times as long as wide; palpus about as long as 1st flagellomere. Thorax with 4 narrow longitudinal dark brown vittae, an inner vitta about 1/5 and outer one about 1/3 as wide as pruinose portion between inner and outer vittae on presutural scutum; scutellum reddish yellow at apex. Proepisternum bare; 1 presutural and 1−2 postsutural acrostichal setae; 3 presutural and 3 postsutural dorsocentral setae; 1−2 postsutural intra-alar setae; 2−3 supraalar setae; 2 katepisternal setae. Wing brownish, tegula reddish yellow, basicosta brown to dark; costal spine about 1.5 times as long as crossvein r-m. Lower calypter with long fringe on outer margins. Legs reddish yellow, claws and pulvilli about as long as tarsomere 5; mid tibia with 2−3 posterodorsal setae; hind tibia with 2−3 anterodorsal, 2 posterior and 2−3 ventral setae. Abdomen reddish yellow in ground color, widely black on mid-dorsal longitudinal portion, and black on posterior margin of tergites 3 to 5; dorsum entirely covered with grayish white pruinosity, sometimes broadly bare on posterior sides of tergite 3. Syntergite 1+2 with a lateral marginal seta, without median marginal setae; tergite 3 with 2 pairs of median discal, 1 pair of median marginal and 2 lateral marginal setae; tergite 4 with 2 pairs of median discal and a row of marginal setae; tergite 5 with some discal and a row of marginal setae. Male terminalia. Posteror lobe of sternite 5 rounded apically; apical half of cerci slender, pointed at apex; surstylus long and wide, pointed apically; postgonite distinctly shorter than basiphallus.

Female. Frons about 0.38 times as wide as head width; gena 0.6−0.7 times as wide as eye height; 7−8 inclinate frontal setae; 2 strong proclinate orbital setae; 1 upwardly directed prevertical seta; inner vertical seta longer than ocellar seta and as long as upper frontal setae. Thorax with gray pruinosity. Abdomen entirely covered with grayish white pruinosity; tergites 3 with 1 pair of median discal setae, tergite 4 with or without discal setae; tergite 5 without discal setae, some median setae of marginal setae shifted forward. Other characters almost same as in male.

Type material. Syntypes of Musca vacua Fallén , Sweden ( SMNH) (not examined) .

Material examined. FRANCE. 1 male, 1 female, St. Germain , 11−21.vii.−viii.1951, H.L. Parker, B. Herting det. ( CNC) . SWEDEN. 1 male, Grisslehamn , 2.viii.1925 , Hedqren ; 1 male, Ustharnmea , 31.vii.1935, Hedqren, Bergström det. ( SMNH) .

Distribution.? China; Europe (northwards to Sweden); Russia (North European territory).

Remarks. This species has long been known from Europe and recently found in East Asia. It is similar to D. ventralis , but differs from it in having an undeveloped facial carina and almost entirely grayish white pruinosity on abdominal tergites in male. Chao et al. (1998: 2154), Shi (2004: 90) and Chao et al. (2009: 576) probably misidentified Chinese specimens of D. ventralis as D. vacua .

Host. Scarabaeidae : Serica brunnea L. ( Tschorsnig & Herting 1994: 157).