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Identification & Distribution:


Hybomitra distinguenda is a medium to large horsefly with a body length of 15-18 mm. It has extensive orange side markings on the abdomen extending from tergite 1 to tergite 4 (see first picture below). The extent of the orange side markings distinguishes Hybomitra distinguenda from Hybomitra solstitialis and some forms of Hybomitra bimaculata, which only have orange side markings on tergites 1-3 or 1-2. The eyes of the female of Hybomitra distinguenda are green and have three reddish bands (see second picture below).


Hybomitra distinguenda can be confused with another orange Hybomitra, Hybomitra ciuraei. The only reliable way to separate them is to examine the colour of the hairs on the lateral thirds of the second tergite. In Hybomitra distinguenda they are entirely pale haired over the orange ground colour (or with only an odd dark hair), as can be seen in the picture below. Hybomitra ciuraei has similar orange side markings, but has patches of pale and dark hairs on the lateral thirds of the second tergite. The presence of many golden hairs on the lateral third or more of the abdominal dorsum gives female Hybomitra distinguenda the bright appearance referred to in the English name. The female may have dark hairs on the orange areas near the midline.

The male (not pictured here) has a narrow black stripe on the abdomen tapering to the third tergite. The lateral orange areas of the male are extensively covered with black hairs with only a few yellow hairs, in sharp contrast to the female. The first antennal segment is grey-black and the eyes have the upper facets somewhat larger than the lower, but not sharply segregated.

Distribution & Seasonal Occurrence

The bright horsefly is widespread in Britain and Ireland, although it is scarce in the north. Grayson (2004) reviews the status of Hybomitra distinguenda in Yorkshire in Britain. He concludes it is widely distributed in Yorkshire but very local. Most records came from North East Yorkshire. It is found through most of Europe and in Russia, Mongolia, China and Japan. Ysebaert (1992) notes that Hybomitra distinguenda is a common species throughout Europe inhabiting various types of biotypes. Its habitats include wet heath, bog, wet woodland edge and wet meadows. The flight period early June to late August, peaking in early to mid July (Drake 1991).


Biology & Ecology:

Resting behaviour & Swarming

Stubbs & Drake (2001) describe males hovering in woodland glades in early morning sunshine, presumably prior to mating. Males of many species form daily hovering aggregations, within which they pursue, capture and copulate with passing females (Wilkerson, 1985). Hovering occurs at species specific locations and times. Grayson (1997b) has observed Hybomitra distinguenda hovering at a height of about 2 metres, above boggy ground in Yorkshire. He also regularly found males on the middle fence rails during mid morning.

Blood feeding

Hybomitra distinguenda is thoughts to feed opportunistically on large mammal species (deer, cattle, horses), although no blood meal analysis has been carried out to determine feeding patterns of this species. Titchener et al. (1981) reports catching a few Hybomitra distinguenda around cattle in Scotland. Ysebaert (1992) records it biting a donkey as well as attacking man.

Grayson (1997a) reports that females generally attack in ones and twos, encircling the legs and lower torso several times before alighting. Several of the Yorkshire records for the species by Grayson (2004) are of attacks by Hybomitra distinguenda on the recorder.

Nectar feeding & puddling

Both male and female Hybomitra distinguenda take nectar from flowers (Kniepert, 1980) as well as blood from mammalian hosts. Goffe (1935) describes males of this species dipping over water.

Breeding sites

In Japan Inaoka (1992) reports that Hybomitra distinguenda is anautogenous. A rare report of eggs of Hybomitra distinguenda is given by Hayakawa & Inaoka (1989) They found egg batches on Carex vesicaria in sunny places in Hokkasido from mid-July to early August. The egg batches were enamelled black in colour, with an average of 224 eggs with 1 to 3 layers of eggs. The eggs of another species, Hybomitra takahasii were parasitized by hymenopterous egg parasites, but those of Hybomitra distinguenda were not.

Trapping & odour attractants

There seems to have been very little work comparing odour baits for Hybomitra distinguenda, although Inaoka (1975) used dry ice (carbon dioxide) as an attractant with traps for the species in Japan.

Using cow urine/acetone - baited NG2F traps in southern England, we have found the species in a variety of habitat types ranging from meadows to open woodland (Brightwell & Dransfield, 2014). Highest catches were in mixed coniferous-deciduous woodland in East Sussex where traps were set in woodland rides (see below). It was the commonest tabanid species after Tabanus bromius.

The only place the species was completely absent was in coastal grazing land & salt marsh. At Rye Harbour in East Sussex it's niche was apparently taken by another much rarer Hybomitra species, Hybomitra ciuraei.


  • Brightwell, R. & Dransfield, R.D. (2014). Survey of Tabanidae (horseflies) in southern England 2014. A preliminary survey of tabanids using odour-baited NG2F traps. 14 pp. Full text

  • Drake (1991). Provisional Atlas of the Larger Brachycera of Britain and Ireland. Institute of Terrestrial Ecology. NERC. Full text

  • Goffe, E.R. (1935). Male Tabanidae (Dipt.) in the New Forest, Hants, 1933-34. J. Soc. Br. Ent. 1(4), 100-109.

  • Grayson, A. (1997a). Personal notes on attacks by female tabanids. In: Larger Brachycera Recording Scheme Newsletter 15Full text

  • Grayson, A. (1997b). Further notes regarding finding male tabanids. In: Larger Brachycera Recording Scheme Newsletter 15Full text

  • Grayson, A. (2004) A review of the Yorkshire status of Hybomitra distinguenda (Verrall, 1909) (Diptera: Tabanidae). Larger Brachycera Recording Scheme Newsletter 23Full text

  • Hayakawa, H. & Inaoka, T. (1989) . Plants as oviposition sites of Hybomitra distinguenda (Verrall, 1909) and Hy. takahasii Inaoka et Hayahaw, 12982 and their egg batches (Diptera: Tabanidae). Japan Society of Medical Entomology and Zoology 40(1), 61-63. Abstract

  • Inaoka, T. (1975). Habitat preference of tabanid flies in Hokkaido based upon the collection of female adults. Jour. Fac. Sci. Hokkaido Univ. Ser. VI. Zool. 20(1).

  • Inaoka, T. (1992). Reproductive life histories of hematophagous tabanids (Diptera: Tabanidae) in Hokkaido with special reference to their autogeny. Japanese Journal of Sanitary Zoology 43(3), 177-193. Full Text

  • Kniepert, F.W. (1980). Blood-feeding and nectar-feeding in adult Tabanidae (Diptera). Oecologia 46, 125-129. Abstract

  • Stubbs & Drake (2001). British Soldierflies and their allies. British Entomological and Natural History Society.

  • Titchener, R.N. et al. (1981). Flies associated with cattle in south west Scotland during the summer months. Researches in Veterinary Science 30(1), 109-113. Abstract

  • Wilkerson, R.C. et al. (1984). Swarming, hovering and mating behaviour of male horse flies and deer flies (Diptera: Tabanidae). Fla. Agr. Exp. Stat. J. Series No. 3953.

  • Ysebaert, T. et al. (1992). A contribution to the horse fly fauna of the Ardeche (France) (Diptera: Tabanidae). Phegea 16(1), 13-17. Full text