Twin-lobed deer-fly

Twin-lobed Deer-fly

Twin-lobed Deer-fly ©Les Binns

Twin-lobed deer-fly

Scientific name: Chrysops relictus
Many of us have felt the painful bite of the Twin-lobed deer-fly (a 'horse-fly') while out walking in damp grasses or woods. But mostly, it prefers to feed on the blood of cows and ponies, often becoming a pest.

Species information


Length: 1cm

Conservation status


When to see

May to September


The Twin-lobed deer-fly is a species of horse-fly and, as such, the females have sharp, biting mouthparts and feed on the blood of large mammals, such as cows and ponies, 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 predate other invertebrates. This biting insect can be a real nuisance during the summer, especially in hot, thundery weather.

How to identify

Up-close, the Twin-lobed deer-fly is a beautiful horse-fly, with a yellow-and-black body, patterned wings and iridescent green-and-red eyes. There are 30 species of horse-fly in the UK; this is one of the most frequently encountered species in damper habitats.



Did you know?

Unlike cleg-flies, the Twin-lobed deer-fly buzzes when it moves, so can be heard coming by its prey!

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.