Notch-horned Cleg-fly

Notch-horned Cleg-fly ©

Notch-horned Cleg-fly

Scientific name: Haematopota pluvialis
Many of us have felt the painful bite of the Notch-horned Cleg-fly (a 'horse-fly') while out walking in grasslands or woods. But mostly, it prefers to feed on the blood of cows and horses, often becoming a pest.

Species information


Length: 1cm

Conservation status


When to see

May to September


The Notch-horned Cleg-fly is a common species of horse-fly that lives in long grassland and damp woodland habitats. The females have sharp, biting mouthparts and feed on the blood of large mammals, such as cows and horses, but will also happily drink the blood of humans. The males lack these mouthparts, so feed on nectar. Females wait in shady areas for their prey to pass-by, locating it by sight with their large, compound eyes. The eggs are laid on stones and plants, or in mud, close to water. When the larvae hatch, they fall on to the damp earth where they predate other invertebrates. This biting insect can be a real nuisance during the summer, especially in hot, thundery weather.

How to identify

The Notch-horned Cleg-fly is dark grey in colour, with grey-brown mottled wings and intricately striped, iridescent eyes. There are 30 species of horse-fly in the UK; this is one of the most frequently encountered species and also one of the smaller ones.



Did you know?

Unlike other horse-flies, cleg-flies are silent in flight, creeping up on their unsuspecting prey. Continuing their sneaky strategy, they usually try to get their meal before the prey notices the pain of the bite, the sharpness of which also distracts them from swatting the biter.

How people can help

The Wildlife Trusts work with pest controllers to find the most wildlife-friendly solutions to some of our everyday problems. We also recognise the importance of healthy habitats to support all kinds of species throughout the food chain, so look after many nature reserves for the benefit of wildlife. You can help too: volunteer for your local Wildlife Trust and you could be involved in everything from coppicing to craft-making, stockwatching to surveying.