Species Spotlight: Great Pied Hoverfly
Time for the second part of our Species Spotlight double header this week! Today we are looking at rachall1's great pied hoverfly, also known as the pellucid fly, (Volucella pellucens) observation.
I want to talk about this species because it is part of a family of insects that is not championed as much as it should be...
V.pellucens is part of the hoverfly insect family (Syrphidae). This is a family in the fly order (Diptera), which includes the common house fly. This order has only one pair of wings, unlike the rest of the winged insects, which have two pairs. There are over 270 hoverfly species in the UK and about 6,000 species globally. Most have wonderful, unique patterns, making them popular among insect-spotters. V.pellucens has a gorgeous large cream band around the middle of its abdomen, which, in certain lights, is translucent, allowing you to see through the insect! (Hence the name "pellucens", from the word "pellucid")
Hoverflies are often mistaken for bees or wasps because most hoverflies have yellow and black colouring, similar to their hymenopteran counterparts. However, you can easily spot a hoverfly on the wing (i.e. whilst it's flying) because of their unique flying style - often they can be seen hovering around flowers (hence the name), and when they're flying about they tend to zip quickly from place to place, hovering in between, in contrast to bees and wasps, which tend to be a bit more amble-y* and less straight-line-y when flying*.
- surprisingly, these aren't proper entomological terms
What you'll notice in rachall1's picture is that V.pellucens has a really large, striking pair of eyes. These eyes likely look familiar, as they are characteristic of the Diptera order. This is another easy way to tell hoverflies apart from bees and wasps - flies' eyes are positioned on the top of the head, forward facing, whereas bees and wasps have eyes on the side of their head.
So now you know how to spot the difference between those yellow and black things buzzing around your garden. But why do hoverflies look like bees and wasps in the first place? It's all to do with protecting themselves....
In biology, we use the term "mimicry" to describe situations where different organisms resemble each other. These resemblances don't have to be visual - they can also be acoustic or chemical or tactile. There are several reasons why they may have evolved to do this (because it is almost always an evolved trait, rather than chance), but they generally fall into three main camps: defensive (pretending you're dangerous), aggressive (pretending you're not dangerous), or reproductive (pretending you're... well you can fill this in yourself).
Hoverflies' mimicry falls into the first camp - hoverflies are NOT harmful at all, but they mimic bees and wasps, which can be dangerous to other animals due to their sting. They do this to avoid predation - by looking like potentially dangerous bees/wasps, they are trying to fool would-be predators into avoiding them. When the mimic organism looks like the thing it's copying, but does NOT share its dangerous/unpalatable attributes, it is known as BATESIAN MIMICRY, after Henry Walter Bates who hypothesised the anti-predator adaptation of some mimics. Another way of thinking of Batesian mimicry is a "sheep in wolf's clothing".
Mimicry is a huge and really, really fascinating topic in biology, which I will try to return to in a future blog post, but for now let's look at why hoverflies are really important insects for humans....
Hoverflies are very important pollinators, second only to bees! Hoverfly pollination is nowhere near as well-studied by scientists or as well-known by the public, but it is absolutely crucial for our ecosystems. I think all the wonderful "SAVE THE BEES" messaging really should say "SAVE THE BEES AND HOVERFLIES". Furthermore, whilst adult hoverflies tend to feed on nectar and pollen, the larvae of many species are voracious insectivores (they love eating insects), with aphids and other crop pests being among their favourite prey. As such, they are brilliant biological controls, keeping pest populations in check, meaning they are very important to farmers around the world, saving food and money. Hoverflies are brilliant!
Let's finish by talking a little more about V.pellucens. This is a widespread species, being found across the UK, the rest of Europe and parts of Asia, and is typically found in hedgerows and woodlands. Adults are generalist pollinators, meaning they are not fussy about which flowers they visit. One of the coolest things about V.pellucens is that its larvae live in the underground nests of the common wasp (Vespula vulgaris). Adult female V.pellucens enters the nest to lay her eggs. Once they hatch, the larvae feed on the wasp larvae and any dead adults.
So there we have it - hoverflies are gorgeous, harmless (if you're not wasp larvae, which I don't think any of your are), and very very important! If you're interested in finding out more about these brilliantly-patterned creatures, there are some great Facebook groups, such as UK Hoverflies.
Enjoy the sun over the bank holiday weekend - a perfect chance to do some spotting!
Kieran
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