Marmalade Hoverfly

Episyrphus balteatus — the marmalade hoverfly — is one of the most ABUNDANT and most ecologically important migratory insects in temperate Europe and one of about 6,000 species in family Syrphidae (the hoverflies). The species is widespread across Europe, North Africa, central Asia, and Australia. Adults are 7-12 mm long with bold black-and-yellow banded abdomens that closely resemble a small wasp (Batesian mimicry — adult hoverflies have no sting and are completely harmless, but bird and mammalian predators avoid them with the same caution applied to actual stinging vespids). The species' migration biology is one of the most spectacular insect migrations ever documented. Wotton et al. (2017-2019, Cell Current Biology and other journals) used radar tracking studies of high-altitude insect migration over Britain to demonstrate that approximately 4 BILLION marmalade hoverflies migrate annually across Britain alone — making the species the most abundant migratory insect ever measured by radar. The migration is multi-generational: spring northbound migrants from Mediterranean overwintering grounds breed in temperate Europe, summer offspring continue the migration further north or stay to breed, autumn southbound migrants return to overwintering areas. The same study estimated that the European hoverfly migration transports 80 MILLION TONS OF POLLEN ANNUALLY across the continent — contributing to pollination at the same scale as honey bees but spread across vastly more flower species and across vastly larger geographic distances. The species is therefore one of the most ecologically important pollinators in Europe — a fact that has been substantially under-recognized historically because hoverflies are individually less efficient pollinators than bees but vastly more abundant. Larvae are equally important as APHID PREDATORS — each larva consumes 200-1,000 aphids over a 2-3 week development period before pupating, making the species one of the most beneficial natural-control agents of aphid pests in European gardens and agriculture.