Gasterophilidae Girschner, 1896

Medium-sized to large, rather thickset flies, the body covered with dense short or longer hairs, without thick bristles. Body length of Gasterophilus species 9.0-16.0 mm, of other genera 11.0-35.0 mm. Body colour of European species brown and yellow, often spotted. Mouth parts in adults entirely absent or, in certain species, only small vestiges retained. Ocelli developed, absent only in the genus Gyrostigma. Perpendicular suture on mesonotum interrupted in middle. Wing long, vein M moderately curved to the rear. A strong non-projecting ovipositor is characteristic of females, formed by the narrow and twisted sixth and seventh abdominal segments and bent beneath the abdomen.

The body of the larva is spindle-shaped, and oral hooks are developed in all instars. The anterior edge of the body segments bears transverse lines of sclerotized spines. The posterior peritremes are joined into one plate, placed in the cavity of the last segment; second instar larva with two, third instar larva with three, vertically placed respiratory slits on each side.

Bot flies are specific parasites of Perissodactyla and Proboscidea. Females lay eggs on the hairs or skin of their hosts, or in some cases on grass. The biology of individual genera and species differs, but a common feature is their development in the gastrointestinal tract of their hosts. First instar larvae enter the host´s mouth when the host licks skin, or they are active on the surface or enter through the top layer of the skin; in G. pecorum they are ingested with the grass of the host's food. Second and third instar larvae of most species live as parasites in the stomach. Larvae leave the host's body with the faeces and pupate in the soil. Adults do not feed and live for only a few days in the summer. They fly at great speed, some 80 km/h, and torment their hosts. In the temperate zone, Gasterophilus species produce one generation per year. Bot flies cause economic damage to the livestock breeding industry (Minář 1980).

15-20 species in 5-7 genera (according to different classifications) are known from the Palaearctic, Afrotropical and Oriental regions, of which six species in the genus Gasterophilus are known in Europe. Data on the systematics, morphology and biology of the family can be found in several monographs (Zumpt 1965, Minář 1980, 2000, Soós & Minář 1986, Papp & Szappanos 1992). Altogether four species are known from the Czech Republic and Slovakia, where the family is well known (Minář 1980, 1997).