Dexia bivittata ( Townsend, 1928 )

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 : 17-19

Dexia bivittata ( Townsend, 1928)

Figs. 9−12

Barydexia bivittata Townsend, 1928: 380 . — Baranov 1932: 215.

Dexilla bivittata: Crosskey 1967: 106 .

Dexia bivittata: Crosskey 1976: 178 .

Diagnosis. Prementum about 6 times as long as wide; thorax with 2 broad longitudinal black vittae; wing dark on median portion, costal spine short; legs black; abdominal syntergite 1+2 without median marginal setae; tergites 3 and 4 usually without discal setae; surstylus narrow and pointed apically.

Description. Body length. Male: 13.5−14.5 mm, female: 8.8−12.7 mm.

Male. Head with dense pale grayish white pruinosity, yellowish on fronto-orbital plate; frontal vitta black; gena brown, with thin pruinosity; 1st flagellomere reddish yellow, pedicel brown; palpus yellowish brown on apical 1/3 and brown on basal 2/3. Frons 1/6−1/7 head width; parafacial nearly parallel-sided, 3−4 times as wide as 1st flagellomere; facial carina long and high, rather flattened on ridge, arched in lateral view; gena about 0.5 times as wide as eye height or slightly more; lower margin of face well protruded. Inner vertical seta about 0.4 times as long as eye height and shorter and weaker than upper frontal setae; outer vertical seta slightly less than 1/2 as long as inner seta; ocellar seta as long as, or slightly longer than inner vertical seta; 11−12 strong frontal setae, lowest seta nearly level with base of pedicel; fronto-orbital plate with a few fine short hairs among row of frontal setae; parafacial bare; gena only with a row of fine and short setae on lower portion; vibrissa inserted above level of lower margin of face by about length of pedicel. Antenna falling short of lower margin of face by 1/2 length of 1st flagellomere, 1st flagellomere 4−5 times as long as pedical; arista long plumose, total width of arista including plumosity about 4 times as wide as 1st flagellomere. Prementum about 6 times as long as wide and more than 1/2 eye height; palpus as long as antenna.

Thorax black in ground color, scutum with dense grayish white or pale yellowish white pruinosity, 1 pair of broad longitudinal black vittae extending to anterior margin of scutellum, posterior margin of postsutural scutum and supra-alar area, base of Wing and postalar callus dark brown, longitudinal vitta about twice as wide as pruinose portion between the vittae; scutellum with dense grayish white or pale yellowish white pruinosity on apical 3/4; pleura with rather dense grayish white, somewhat silvery, pruinosity on upper 2/3 of proepisternum, posterior 2/3 of anepisternum, 2/3 of katepisternum, anterior and posterior 1/3 of meron and anatergite; brownish on other portion. Proepisternum bare; 2−3 postpronotal setae; 1 presutural and 2 postsutural acrostichal setae; 3 presutural and 3 postsutural dorsocentral setae; 1 postsutural intra-alar seta; 3 supra-alar setae, anterior one about 1/2−3/4 as long as posterior setae; 3 katepisternal setae. Wing tinged with pale reddish brown on humeral cell and basal 1/2 area of basal cell, pale brownish on other area except darker median portion, alula pale brown; tegula and basicosta dark brown; calypters yellowish brown. Costal spine absent or very short, shorter than 1/2 length of crossvein r-m; relative lengths of 2nd, 3rd and 4th costal sectors approximately 3:6:2.5; short M appendix sometimes present, vein M from dm-cu crossvein to its bend about 4 times distance between the bend and wing margin. Lower calypter with long fringe on outer margin. Legs dark brown; mid leg longest; hind tibia straight; mid tibia with 2−3 posterodorsal setae; hind tibia with 2−3 anterodorsal, 2 posterodorsal and 1 ventral seta.

Abdomen long ovate, translucent reddish yellow in ground color, darkened on median depression and posterior 1/5 of syntergite 1+2, posterior 1/5−2/5 of tergite 3, and posterior 1/3−1/2 of tergite 4; pruinosity indistinct on tergites 3 and 4, and only thinly visible on anterior 2/3 of tergite 5. Hairs black, dense fine short and suberect on dorsum and long on lateral portion; syntergite 1+2 with 1 lateral marginal seta, without median marginal setae; tergite 3 with 1 pair of median marginal and 1 lateral marginal setae, without median discal setae; tergite 4 with or without a pair of fine median discal, and with a row of strong marginal setae; tergite 5 with regular rows of discal and marginal setae. Male terminalia. Surstylus slender, apex slightly pointed, with dense setulae; cerci slender on apical 3/5; postgonite slightly shorter than basiphallus; distiphallus slender.

Female. Smaller than male; fronto-orbital plate yellowish; frons 1/3−1/4 head width, 7−8 inclinate frontal setae, 1 reclinate prevertical and 2 proclinate orbital setae; mid tibia with 2 anterodorsal and 2 posterodorsal setae. Abdomen ovate, reddish brown in ground color, with yellowish white pruinosity on tergites, dark brown on posterior margin of syntergite 1+2, on posterior 1/3 of tergites 3 and 4, tergite 3 with a black longitudinal vitta, tergite 5 with yellowish white pruinosity. Other characters same as in male.

Type material examined. Lectotype male of Barydexia bivittata Townsend (by designation of Crosskey 1976: 178), PHILIPPINES, Mt. Banahao , P.I. Baker ( USNM).

Additional material examined. PHILIPPINES. 11 males, 3 females, Lake Binado– Summit, Mt. Apo, 1350−2850 m, Mindanao , 4−5.viii.1978, A. Nakanishi and O.Yata ( BLKU) . 1 male, Baguio, Benguet, Baker ( USNM) . 2 males, Mountain Province, Mayoyao , Ifugao, 1200−1500 m, 28.vii.1966, 10.viii.1966, H.M. Torrevillas . 1 female, Bukidnon, 1250 m, Mt. Katanglad, Mindanao , 4−9.xii.1959, L.W. Quate ( BPBM) .

Distribution. Philippines (Luzon, Mindanao).

Remarks. This species was described from an unknown number of specimens. Townsend (1938: 320) designated a “Ht male” from “Mount Banahao, Luzon”, but this is not accepted as a valid lectotype fixation following O’Hara et al. (2009: 11). Crosskey (1976: 178) examined the “ Lectotype ” male of Sumatrodexia bivittata Townsend in USNM and this is accepted as the lectotype fixation.

This species is similar to D. longipes , but is distinguished from it in having 1 pair of broad longitudinal black vittae on thoracic dorsum, 3 presutural and 3 postsutural dorsocentral setae, thorax and abdomen with black hairs, abdominal syntergite 1+2 without median marginal setae, and surstylus pointed apically.