This Insect Week (June 23^rd to 29^th), The Wildlife Trusts and Royal Horticultural Society are asking gardeners to look out for hornet look-a-likes, as part of their ‘Be a hoverfly hero’ campaign.

According to insect experts at the two organisations, nature can be canny: what you think is a hornet may be a hoverfly disguised as its more fearsome fellow pollinator – both do important jobs in your garden.

These creatures are deploying a cunning art – Batesian mimicry – named after explorer Henry Walter Bates. Whilst exploring Amazon rainforests, he noted that many species had evolved to look scarier than they actually were, to avoid being eaten by predators.

Tom Hibbert, manager of Wild About Gardens for The Wildlife Trusts, says:

“With occasional media reports of the newly arrived yellow-legged hornet (also referred to as the Asian hornet), which feeds on bees, our native European hornet is in danger of getting a bad name. In truth, our native hornets – while larger – are less aggressive than wasps and they are useful pollinators too.

“There are also wonderful hoverfly hornet mimics, which have no sting and are busy pollinating our plants. With so many natural predators, who can blame them for wanting to appear more intimidating than they really are.”

Concern about hornets has been heightened since yellow-legged hornets were spotted in Gloucestershire in 2016. Sightings of these invasive insects which feed on up to 50 honeybees a day are still limited but they have been rising, with fifteen captured this year and a nest destroyed in Kent.

Conversely, hoverfly numbers have been damaged by harmful pesticides, urban development and climate change. In 2022 the International Union for the Conservation of Nature added hoverflies to its Red List of threatened species. 

Five ways to identify whether you are looking at a real hornet or a hoverfly mimic:

• Wings: Hoverflies have one set of wings, whereas hornets have two.
• Eyes: Hornets have five eyes – a compound eye on each side of the head and three simple eyes in between. Hoverflies have just two large, round eyes which are prominent and visible from above.
• Size: Hornets are larger than wasps, reaching up to 4cm in length. Hoverfly hornet mimics reach only around 2cm in length.
• Shape: Hornets have tiny waists like wasps but hoverflies are curvier.
• Colour: All these insects feature black and yellow stripes but invasive yellow-legged hornets are predominantly black, with just one large yellow stripe, and have bright yellow legs. 

Helen Bostock, senior wildlife expert at the Royal Horticultural Society, says: 

“Nature has a way of pulling the wool over our eyes and hoverflies have so many delightful disguises – they can imitate bees, wasps and, yes, even hornets. You can encourage hoverflies into your garden by planting open, easily accessible flowers. This summer, they’ll love blackberry flowers, oxeye daisy, marigold, fennel, cow parsley and poppies. Come autumn, they’ll be seen on heather, aster and even common ivy.”

Find out more about hornet identification and how to report a sighting of a yellow-legged hornet.