Coenosia trina WIEDEMANN, 1830

Hänel, Christine & Pont, Adrian C., 2008, Houseflies of the Tristan da Cunha Islands: new records, including the first for Fannia albitarsis S, 1911 (Diptera: Fanniidae, Muscidae), Beiträge Zur Entomologie = Contributions to Entomology 58 (1), pp. 211-222 : 216-217

Coenosia trina WIEDEMANN, 1830

First recorded (as C. humilis MEIGEN, 1826 ) from Tristan by BAIRD (1965: 426) and HOLDGATE (1965: 397), and from Nightingale by CARVALHO & COURI (1999: 211-212).

Widespread in the Afrotropical region. Adults of its sister-species, the Holarctic and Oriental C. humilis , with which it probably shares its biological features, are voracious predators of other small soft-bodied insects ( EVANS, 1930; KÜHNE, 2000). Larvae of humilis are also predaceous, and most probably live in soil. In the laboratory, KÜHNE (op. cit.) was able to maintain cultures on a substrate of wood bark fibre to which crushed oats were periodically added, where they fed on introduced prey larvae.

This species was, under the name of multimaculata ADAMS, 1905, ranked as a subspecies of Coenosia humilis MEIGEN by EMDEN (1940: 179) since there were consistent but small differences between European and Afrotropical humilis . It was still ranked as a subspecies of humilis by PONT (1980b: 755), with trina WIEDEMANN, 1830 , listed as a doubtful synonym. Since then, the typeseries of trina has been examined and the availability of this name for the Afrotropical vicariant of Coenosia humilis established ( PONT, 1997: 113-114). Study of the present material strongly confirms that trina should be ranked as a species distinct from humilis , based on the characters given by EMDEN (l.c.), especially the slightly longer haired arista in trina , the narrower frons in trina , and the generally more extensive dark dusting on scutellum and abdomen in trina .

461 specimens collected in 2005; 39 on Tristan (21 ♂♂, 18 ♀♀), and 422 on Nightingale (191 ♂♂, 231 ♀♀) .

TRISTAN DA CUNHA, west of Edinburgh village , potato patches, cultivated cropland, potatoes, vegetation and cattle grazing, 37°09'06"S 12°34'26"W, 07-12.ii.2005, Malaise, site 2, sample 14c, C. HÄNEL, 1 ♂, 1 ♀ (pinned) .

TRISTAN DA CUNHA, up Molly Gulch , on rim, below Dailies Hill, grassland mix, ± 2270 ft., 37°11'44"S 12°33'53"W, 15-21.ii.2005, Malaise, site 7, sample 19, C. HÄNEL, 3 ♂♂ (alcohol) .

TRISTAN DA CUNHA, Sandy Point , woodland shrub, behind the hut, ± 102 ft., 37°11'47"S (dubious) 12°22'61"W, 21.ii.2005, site 9, sample 22, C. HÄNEL, 17 ♂♂, 17 ♀♀ (alcohol) .

NIGHTINGALE, Path up from West Landing, coastal cliffs cave-overhang with tussock, 37°24'98"S 12°29'09"W, 3-4.iv.2005, Malaise, site 6, sample 22, C. HÄNEL, 3 ♀♀ (alcohol); site 6, sample 23, Malaise, 52 ♂♂, 77 ♀♀ (alcohol) .

NIGHTINGALE, West Road , path inland from landing, tussock grassland some Scirpus and alien spp. in path, 37°25'02"S 12°28'66"W, 28-29.iii.2005, Malaise, site 7, sample 19b, C. HÄNEL, 7 ♀♀ (alcohol); site 7, sample 21, Malaise, 4 ♂♂, 1 ♀ (alcohol) .

NIGHTINGALE, Herbert’s hut site, East landing area, tussock grassland and alien veg. along path, 37°25'08"S 12°28'53"W, 29-31.iii.2005, Malaise, site 3, sample 20a, C. HÄNEL, 85 ♂♂, 95 ♀♀ (alcohol) .

NIGHTINGALE, 3rd Pond close to top of path, mire wetland, Scirpus spp. , fernbush spp. and mosses, 37°25'53"S 12°29'10"W, 26.iii.2005, sweep-netting, site 10, sample 58, C. HÄNEL, 2 ♂♂, 2 ♀♀ (alcohol); 26-28.iii.2005, Malaise, site 10, sample 51, 34 ♂♂, 38 ♀♀ (alcohol) .

NIGHTINGALE, 1st Pond, furthest from path, mire wetland with pool surrounded by Scirpus spp. , 37°26'02"S 12°29'30"W, 30.iii-01.iv.2005, site 8, sample 80c, C. HÄNEL, 1 ♂ (pinned); and site 8, sample 55, sweep-netting, 13 ♂♂, 8 ♀♀ (alcohol) .