Curious Questions: Do the disguises of hoverflies really keep them safe from predators?

Hoverflies mimic bees, wasps and all manner of other insects in order to put off predators — but does their subterfuge really work? Simon Morton finds out.

Out in the gardens of Britain at the moment you’ll see dozens of bees, wasps — and hoverflies, those curious, stingless little fellows who pretend to be one or the other with their black and yellow outfits.

As it happens, black and yellow is just one of their many liveries. This is an astonishingly varied beast with 276 different species in Britain alone, and around 6,000 more known across the world. They’re arguably the most colourful and varied tribe to take to the air — even more so than butterflies (56 members), ladybirds (46), dragonflies (30) and damselflies (16), all of which flaunt their identities.

What they’re most famous for, however, is their mimicry of their stinging cousins. And while the difference between bee, wasp and hoverfly is almost immediately obvious to the human eye, there is absolutely no doubt that their disguise helps enormously in keeping them safe from predators.

With not a sting or a bite between them, hoverflies pretend to be honeybees, bumblebees, blowflies or wasps as they work wildflowers and borders or invade greenhouses (in America, they are known as flowerflies).

Active from March to November, they sup nectar, pollen and honeydew, performing as much pollination as their better-known counterparts, although some feed on aphids and dead insects. An opportunistic bird or spider might take rare advantage — one researcher’s tame flycatcher was seen to rub the stings off bees, but take no such precaution with bee-like hoverflies — but fungal infection is their principal enemy.

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A hoverfly dangles from a flower. Photo by VCG / Getty Images.

They’re far from alone in this cleverness. Mimicry in Nature has been well documented, some of which are bewilderingly cunning. There are female fireflies which imitate the mating signals of another species to attract males, which they then eat; the chameleon vine adapts the colour and shape of its leaves to simulate those of its host plant, and thus avoid herbivores; and then there are the fungi which mimic the odour of rotting carrion, thus attracting flies that will disseminate their spores.

There are actually different categories of mimicry bearing the names of the men who classified them. Browerian involves the same species: some caterpillars of the monarch butterfly eat a toxic variety of milkweed and themselves become toxic, so deterring predators from taking others from non-toxic plants. Mullerian involves two species imitating their warning characteristics to mutual advantage, as practised by some ladybirds.

But the big one is Batesian defensive mimicry, whereby vulnerable species take on the appearance of others that predators know to be dangerous. This is the trick pulled off by hoverflies, and is named after Henry Walter Bates (1825–92), one of those redoubtable Victorians who explored the secrets of regions unknown.

Bates spent 15 years documenting insects in the Amazon, determining, among other things, that some butterflies adopted the appearance of unrelated species for their own protection. He delivered his theory to the Linnean Society in London in 1861 and published a paper that established his name and legacy. He deserves to be better remembered.