Genus Gasterophilus Figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19; Table 1

Gasterophilus Leach, 1817: 2. Type species: Oestrus equi Clark, 1797 [= Oestrus intestinalis De Geer, 1776], by subsequent designation of Curtis (1826: 146).

Gastrus Meigen, 1824: 174. Type species: Oestrus intestinalis De Geer, 1776, by subsequent designation of Coquillett (1910: 546).

Gastrophilus Agassiz, 1846: 160. Unjustified emendation of Gasterophilus Leach, 1817. Type species: Oestrus equi Clark, 1797 [= Oestrus intestinalis De Geer, 1776] (automatic).

Enteromyza Rondani, 1857: 20. Unnecessary new replacement name for Gastrus Meigen, 1824 and Gasterophilus Leach, 1817. Type species: Oestrus equi Clark, 1797 [= Oestrus intestinalis De Geer, 1776] (automatic).

Rhinogastrophilus Townsend, 1918: 152. Type species: Oestrus nasalis Linnaeus, 1758, by original designation.

Enteromyia Enderlein, 1934: 425. Type species: Oestrus haemorrhoidalis Linnaeus, 1758, by original designation.

Stomachobia Enderlein, 1934: 425. Type species: Oestrus pecorum Fabricius, 1794, by original designation.

Haemorrhoestrus Townsend, 1934: 406. Type species: Oestrus haemorrhoidalis Linnaeus, 1758, by original designation.

Progastrophilus Townsend, 1934: 406. Type species: Oestrus pecorum Fabricius, 1794, by original designation.

Selected references.

Brauer (1863: 53); Zumpt (1965: 111); Grunin (1969: 21); Pont (1973: 698); James (1974: 92); Kettle (1974); Papavero (1977: 19); Wood (1987: 1148); Soós and Minář (1986: 238); Xue and Wang (1996: 2209); Pape (2001); Pape et al. (2017); Otranto et al. (2005); Colwell et al. (2006: 5); Colwell et al. (2007); Felix et al. (2007); Zhang et al. (2012); Huang et al. (2016); Zhang et al. (2016); Li et al. (2018, 2019); Yan et al. (2019).

Diagnosis.

Body covered with dense, yellowish hair-like setae, variously interrupted by reddish-yellow or dark brown (or black) bands (Figs 1 - 10). Facial plate with a narrow median keel. Antennal arista long, slender, gradually tapered and slightly flattened, with short, sparse microtrichia (Figs 1C, F, I, 2C, F, I, 3C, F, I, 7C, F, I, 8C, F, I, 9C, F, I). Proboscis and palpus vestigial, visible as small, yellow or brown knobs. Thorax ground color mainly dark brown or black (Figs 4 - 6, 7A, D, G, 8A, D, G, 9A, D, G). Notopleuron weakly defined. Posterior spiracle open, with short, hair-like fringes, lappets oriented obliquely at an angle of about 45 degrees. Wing vein M almost straight, very slightly curved posteriorly; vein A1 + CuA2 extending to wing margin (Fig. 10). Upper and lower calypters yellowish, fringed with long, whitish, hair-like setae along the external margin. Abdomen ground color yellow, dark brown or black, sometimes with several irregular dark spots (Figs 1A, D, G, 2A, D, G, 3A, D, G, 4A, C, E, 5A, C, E, 6A, C, E, 7A, B, D, E, 8A, B, D, E, 9A, B, D, E, G, H). Male cercus (Figs 11 - 13) broadly connected to its counterpart by a membrane at the base, with a long or short free apex (Figs 11C, F, I, 12C, F, 13C, F, I); surstylus with a rounded or gradually tapered apex (Figs 11B, E, H; 12B, E; 13B, E, H); phallus short, dorsolateral processes of distiphallus reduced, epiphallus absent; pregonite tuberculous; postgonite falcate (Figs 11A, D, G, 12A, D, 13A, D, G); processi longi (remnants of sternite 10) setose, tubercular or elongated (Patton 1937, Grunin 1969). Female terminalia (Figs 14 - 16) gradually tapered, either short and straight (Fig. 9E) or long and curved forward (Figs 7B, E, H, 8B, E, 9B, H); segment 7 modified, fully sclerotized, tube-shaped, dorsally with a longitudinal suture, without separation of tergite and sternite 7; tergite 8 laterally expanded downwards; sternite 8 either with a longitudinal concavity in the middle and with a keel-shaped apex (Fig. 16F), or longitudinally ridged in the middle and with a scallop-shaped apex (Figs 14C, F, L, 15C, F, L, 16C); tergite 10 (epiproct) composed of two approximately triangular sclerites (Figs 14B, E, H, 15B, E, H, 16B, E); cercus long and narrow, narrowly connected to its counterpart by membrane and with a very short prolongation (Figs 14A, D, G, 15A, D, G, 16A, D). Eggs with an attachment organ, short and posteriorly located or elongated and situated ventrally (Figs 17 - 18). The larva with a bilobed, highly constricted pseudocephalon, three thoracic segments, seven abdominal segments, and the anal division divided into three subdivisions (Zumpt 1965; Grunin 1969; Li et al. 2018). The freshly hatched larva fusiform, anteriorly encircled with strong body spinose; posterior spiracles slightly or distinctly elongated, fully exposed, with two serrated margined slits (Zumpt 1965; Grunin 1969). The second and third instar larva sub-cylindrical, with mouth hooks posterolaterally curved and sharply pointed, and a pair of oral plates between mouth hooks; most of the body segments circled anteriorly by strong, posteriorly directed spines arranged in one, two or three rows (Zumpt 1965; Grunin 1969; Li et al. 2018). The third instar larva distinctively colored in red, yellow or green (Li et al. 2018).

Hosts.

Known exclusively from the genus Equus Linnaeus ( Perissodactyla: Equidae). So far, no records have been made from the species E. grevyi Oustalet ( Grévy’s zebra) and E. kiang Moorcroft (kiang or Tibetan wild ass).

Distribution and diversity.

Native distribution matches that of the horse family, currently with highest diversity in China and South Africa, with 7 species recorded, followed by Mongolia, Senegal and Ukraine, with 6 species recorded (Fig. 19). Introduced with domestic hosts to most parts of the world.

Key to adults of Gasterophilus spp.

Key to eggs of Gasterophilus spp.