Tabanids are large biting flies generally called horse flie, Tabanids are medium to very large flies (6–30mm long). The colouration of tabanids varies from very dark brown or black to lighter reddish brown yellow or greenish; frequently the abdomen and thorax have stripes or patches of contrasting colours The head is large and, viewed from above, is more or less semicircular.
Adults are sexed by examining their eyes. In the female there is a distinct space on top of the head separating the eyes: this is known as a dichoptic
. In males the eyes are so large that they occupy almost all of the head and either touch each other on top of the head or are very narrowly separated, this being known as a holoptic.
The antennae are relatively small but stout. They consist of three segments;
the last is subdivided into usually three or four small divisions .
Unlike the Muscidae, Glossinidae and Calliphoridae, there is no antennal arista. The size and shape of the antennae serve to distinguish the genera Chrysops, and Tabanus.
The stout thorax bears a pair of wings which have two submarginal and five posterior cells and a completely closed discal cell in approximately the centre of the wing .Adults at rest have the wings placed either like a pair of open scissors over the abdomen. The presence or absence of coloured areas on the wings and how they are held over the body provides useful additional characters for distinguishing between Chrysops, and Tabanus
they are 1–3mm long, and curved or approximately cigar-shaped. They usually hatch after 5–14 days, the time depending on temperature
Larvae are cylindrical and rather pointed at both ends .They are creamy white, brown or even greenish but often have darkish pigmentation near the borders of the segments. The very small black head can be retracted into the thorax. There are 11–12 well-differentiated body segments.
Larvae are readily recognized by the prominent raised tyre-like rings which encircle most body segments. The first seven abdominal segments have one pair of lateral and two pairs of ventral (a total of six)