The technique is called pool feeding, or telmophagy. The female tabanid's mouthparts include a pair of mandibles that work like small blades, opening a wound in the skin rather than entering a vessel. Saliva containing anticoagulants and vasodilators is introduced so the blood keeps flowing, and the fly takes it up through a sponging labellum. The wound is larger and slower to close than a mosquito puncture, which is why the bite is painful and often continues to bleed.
Males lack the cutting mandibles entirely. They feed on nectar and honeydew, as do females between blood meals, and are frequent flower visitors.
Tabanids are strong fliers, and this has produced one of the most repeated numbers in entomology: a claimed 145 kilometres per hour for a male Hybomitra hinei wrighti, a horse fly, chasing a female. The figure was compiled into the University of Florida Book of Insect Records in 1994 and has never been reproduced by instrumented measurement. It is routinely confused with a separate and far wilder mid-century claim about a deer botfly.