The Relationship between Morphological and Behavioral Mimicry in Hover Flies (Diptera: Syrphidae)

What is it about?

There are lots of ways to fool an observer, including “behavioural mimicry” – where an animal acts like another animal in order to fool a potential predator or prey. This sort of behaviour has been reported plenty of times in the field, but has never been studied in a systematic way. This study provides just such an overview, and tests a few key evolutionary hypotheses along the way. First, though, what does behavioural mimicry look like? In the system that we studied, hover flies (which can’t sting) have evolved to look like wasps and bees (which can sting). The theory is that birds learn to associate the characteristic yellow and black patterns of wasps with a nasty sting and so leave yellow and black insects alone. Hover flies have exploited this and so get eaten less even though they don’t have any form of defence. Some species have also evolved to mimic the behaviours of bees and wasps. These behaviours include: “mock-stinging” (pressing the tip of the abdomen against a surface as if stinging), “wing-wagging” (movement of the wings like a wasp – hard to describe but watch the video in the "Resources" section on the right), and “leg-waving” (waving dark front legs in front of the head to imitate the longer antennae of a wasp). As a result of this study, we now have data on the similarity of behaviours between these two groups. We show that behavioural mimicry is actually relatively rare. Out of 59 species of hover flies, only 6 showed behaviours that looked like wasp behaviours, and those 6 species were restricted to just two genera of hover flies (Temnostoma and Spilomyia). What is most interesting, though, is that these two genera of hover flies are two of the most similar in terms of appearance as well, and we didn’t find any examples of hover flies that don’t look much like wasps but that do show wasp-like behaviour.

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Why is it important?

The work has two key findings: 1 - Behavioural mimicry is relatively rare, even in a group like the hover flies which is quite well known for this sort of mimicry. Furthermore, those species that do show behavioural mimicry are closely related, suggesting a small number of evolutionary origins. 2 - It appears that only those species that have evolved shape and colour like wasps have evolved behaviours like wasps. This suggests that whatever evolutionary pressures drive the evolution of morphological similarity also drive the evolution of behavioural similarity.

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