…or the BFG (Big Friendly Giant) amongst the hoverflies!
When I first encountered the hornet mimic hoverfly (Volucella zonaria) 2 years ago, I thought that it might be able to sting, because of its size (it is the largest hoverfly species in the Netherlands!) and colouration. But upon closer inspection, it turned out to be a harmless hoverfly, which likes to pretend that it is more dangerous than it actually is. Such a phenomenon is called mimicry and this one pretends to be a hornet (as the name suggests).
Unlike the hornet that it mimics, the hornet mimic hoverfly cannot sting or bite, but makes itself useful as a pollinator. The main differences between a hornet and the hornet mimic hoverfly are body size (the hornet is slightly larger and has a pronounced waist), length of antennae (hornet has larger antennae), shape of eyes (the eyes of the hornet mimic hoverfly are more round, whereas those of the hornet are elongated) and the hornet has 4 wings instead of 2.
You might say that it is very easy to distinguish between the hoverfly and the actual hornet, but some research suggests that birds and perhaps other animals are fooled, because some aspects of the hoverfly resemble those of the hornet. Those animals will generally avoid the hoverfly, just like they would avoid a hornet, and leave it alone while it sips some nectar. Better safe than sorry!
An interesting fact about the hornet mimic hoverfly is that it spends its ‘childhood’ as a larvae in wasp nests. Even then it is friendly towards its host, because it eats dead wasps and other waste the wasps produce. Scientists are not entirely sure why and how the hoverfly infiltrates the nest. Especially the how question is of interest, since wasps tend to defend their territory against intruders. Perhaps the hornet mimic hoverfly secretes the same smell as the wasps and by smelling like a wasp, it gets past security checkpoints unnoticed. A spritz of Eau-de-Wasps anyone?
* This is a edited version of my old post, where you can find more information about research on hoverfly mimicry.