Pale Giant Horsefly

• Its bite hurts precisely because it tears rather than pierces, and the wound goes on bleeding because of the anticoagulants in its saliva.
• It homes in on its victims by carbon dioxide, heat and movement, and will chase a running horse or person for tens of metres.
• Its larvae are predatory and live in waterlogged soil, where they hunt earthworms and other larvae.
• Its bite is lacerating in the literal sense: instead of a fine stylet, it has scissor-like mouthparts that slice the skin, and it then laps up the blood that flows. That is why it hurts far more than a mosquito's.
• Only the females bite, and only to mature their eggs; the males sip nectar and cannot bite.
• It locates cattle by carbon dioxide, heat, movement and dark surfaces. That last detail explains why zebras are studied so much: the stripes appear to make it harder for horseflies to land.
• It flies very fast, at up to about 50 km/h, and pursues moving prey, which makes it hard to dodge.
• The wound keeps bleeding after the bite, because its saliva contains anticoagulants, and that favours the mechanical transmission of pathogens between animals.
• Its larvae are predatory and live in damp soils, where they hunt earthworms and other invertebrates.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Damp meadows, riverbanks and grazed pasture in Europe

Sexual maturity

Mating begins in flight and finishes on the ground; only the female bites, because she needs blood to mature her eggs, while the male feeds on nectar and pollen

Gestation / incubation

The eggs hatch between 5 and 7 days; the larva lives in waterlogged soil or in the mud at the bottom of pools and ponds, goes through about eight moults, overwinters as a larva and pupates in spring or early summer

Litter / clutch size

100 to 1,000 eggs per female, in batches of a hundred or so on aquatic vegetation or damp ground, sometimes coated in a glossy or chalky secretion that protects them from the water

Sources consulted: Buglife; Caro et al. (2019), PLOS ONE; Krčmar, trabajos sobre Tabanidae; Cosas de Insectos, ficha Tabano; Mis Animales, ficha Tabanus bovinus; Fichas de biologia de Tabanus; Manual veterinario MSD; Ficha de especie de Tabanus bovinus (clave de Stubbs & Drake 2001)

Best time: Adults in summer, above all on sunny, hot days and in full light. Their activity spikes in the hours before a summer storm, when the pressure drops and the humidity rises