Hornet Robberfly (Asilus crabroniformis) © Steven Falk

Help us track down Hornet Robberflies – a Section 41 Priority species in England and Wales – by submitting your sightings to the Buglife Hornet Robberfly Hunt!

Did you know the Hornet Robberfly (Asilus crabroniformis) is the UK’s largest fly? You can find it on heaths and grasslands in Southern England and West Wales. It relies on grazing animals and insect-rich habitats, hunting beetles, grasshoppers, wasps and flies, and prefers cow pats or horse manure to lay its eggs.

Hornet Robberfly numbers are declining, threatened by habitat loss and changing farming practices – in particular, the use of insecticides such as worming treatments. Since this species cannot fly beyond a few hundred meters from suitable habitat, it has become isolated at around 40 known breeding sites.

Through our ambitious projects, Life on the Edge (South Devon) and Kernow Wyls (Wild Cornwall), we are working to restore and connect wildflower-rich habitats that will help support a diverse range of wildlife and provide a home for rare species such as the Hornet Robberfly to thrive.

But we can’t do this alone. It’s thanks to people power that we can better understand the distribution and density of invertebrate populations today. So, we invite you to become a citizen scientist and share your findings to help us build a bigger picture.

How you can help

By submitting your Hornet Robberfly records, you can help us protect this threatened species. To do this, head over to the iRecord website to submit your findings.

For a visual reference to help you identify the Hornet Robberfly, open our guide below for distinctive features and where you are likely to find them.

View Hornet Robberfly ID Guide

What do they look like?

At 2.5 to 3cm (almost 1 inch) in length, the Hornet Robberfly is the UK’s largest fly. As the name suggests, it mimics the appearance of a hornet to avoid predation while it basks and feeds.

These flies have a bristly and hairy ginger thorax (body section between the head and abdomen) with black and yellow markings on the abdomen (end section of the body), like a hornet. Its legs are long and spiny. When resting, their wings conceal much of their abdomen.

Hornet Robberfly (Asilus crabroniformis) © Laurence Livermore, CC BY-NC 2.0 — Look for the Hornet Robberfly’s spiny legs © Laurence Livermore, CC BY-NC 2.0

Hornet Robberly held between finger and thumb — Hornet Robberfies have long, pointed black and yellow abdomens © Steven Falk

Hornet Robberfly (Asilus crabroniformis) in grass © Will Hawkes — Hornet Robberflies have a ginger thorax © Will Hawkes

When can I see them?

They are active from late July to early October.

Where can I see them?

You will find Hornet Robberflies in or around the vicinity of wildflower meadows and heathland – anywhere where there’s an abundance of insect species and ideally nearby cattle or pastures.

Records show the Hornet Robberfly to be located at sites in Southern England and West Wales which is where we expect sightings to be concentrated. However, if you think you have seen one located further afield, please still send in a photo for us to verify.

Both projects haves been made possible thanks to the National Lottery Heritage Fund. Kernow Wyls has also been kindly funded by Mary Berry’s Salad Dressings, while the partnership project, Life on the Edge, has received additional funding with thanks to the Devon Environment Foundation, Milkywire, and the FatFace Foundation.