SWT: Just pretending, but mimic hoverfly fools hornets

Hornet hoverfly. Picture by Hawk Honey/SWT ANL-140915-155720001
Hornet hoverfly. Picture by Hawk Honey/SWT ANL-140915-155720001
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It’s as big as a hornet. It flies like a hornet. It even looks like a hornet! Yet it’s as harmless as a fly and that’s because it is….er… a fly!

Volucella zonaria or Hornet mimic hoverfly, to give it its common name, is exactly what it says it is – just a mimic. It has no sting and can often be found sunning itself while feeding on a flower.

If one ever comes your way, stop to take a closer look at this jewel of the insect world. The hornet has a waist and visible antennae, the hoverfly doesn’t. As flies go, the hornet hoverfly is pretty impressive at 2cm long. Come late summer, photos of these beautiful creatures start appearing on forums and social media enquiring as to their identity. The adults feed primarily on flowers drinking the nectar and helping to pollinate in the process.

So why does it look like a hornet? There are two good reasons for this. Firstly, looking like a hornet means you’re very unlikely to be predated upon by a bird or a frog – after all hornets have a nasty sting and no predator is going to risk a sting for a snack! But the other reason is that mimicry helps the hoverfly gain access to a hornet or wasp nest – where it prefers to lay its eggs – without being attacked. Hornets guard their nests diligently, attacking any intruder that shouldn’t be there.

The larvae of the hoverfly actually grow up living in the hives of hornets and wasps, feeding off the detritus that gathers in the nest. Sometimes they also eat the larvae of a hornet or two. The hornets don’t seem bothered by this and, although not proven, it is thought that hoverfly larvae only eat diseased hornet grubs and that’s why they get away with it!

Come late summer they emerge from their host’s hive to get on with the important business of pollinating flowers and looking for a mate. The females, easily identifiable because their eyes don’t meet on top of their head like males do, will then find another hive to lay more eggs.