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 & environment

Damp meadows, riverbanks and grazed pasture in Europe

Sources consulted: Buglife; Caro et al. (2019), PLOS ONE; Krčmar, trabajos sobre Tabanidae

Best time: Hot, muggy summer days, near livestock and water