Every summer, with the predictability of hay fever and impromptu barbecues, I am asked by friends, family, strangers and the media: “What’s the point of wasps?”
Although some people will be starting to worry about wasps as they set out their jubilee picnics this bank holiday weekend, wasp complaint season usually kicks off in mid-August in the UK. It’s my summer holiday calibrator, and generally peaks just about the time when I’ve started to unwind from the busy chaos of my life as an academic. I’m not grumbling (my family does that for me); I never turn down the chance to evangelise about wasps. But I am beginning to sound like a stuck record.
So this year I’m doing things differently. I’m preempting late-summer complaints and equipping you upfront with the knowledge you need to understand wasps a little better, in the hope that you will look more favourably at your picnic botherer. The solutions follow the science.
Let’s start with sausages. It makes sense that wasps are after the meat at your barbecue. Adult wasps are hunters; they feed meat to a carnivorous brood. Picnic-bothering social wasps (who live in a colony rather than alone) – Vespula vulgaris and Vespula germanica – are unfussy diners. They hunt flies, spiders and caterpillars – in fact, any creepy-crawly that your garden has to offer. In doing so, they provide you with environmentally friendly pest-control services, free of charge. The average wasp nest in your garden removes about 4.3kg of prey in a lifecycle. This amounts to 9,300 caterpillars, a total of 20,000 bees, wasps and ants, 15,000 flies and 44,000 spiders in an average UK summer. That’s a lot of creatures, many of which would be munching on your lettuces, tomatoes and prize dahlias without wasps to control them.
Your sausages are a convenient protein source for wasps because, unlike flies, they don’t try to escape. Cleaning up dead meat is another important job performed by certain wasps even when it isn’t in sausage form. The cadavers of birds and rats can be stripped clean of meat in a matter of hours by social wasps.
But the scavenging habits of the humble picnic-bothering wasp are a bit unusual. Most wasps won’t take dead meat. And by “most wasps”, I mean the other 100,000 species of wasp that are not the ones you typically notice, at least not in the UK. Seventy thousand of these don’t even have stings: these are the parasitoid wasps who have egg-laying sheaths (ovipositors) which they use to deliver an egg (and some venom) to a live host, like a caterpillar or beetle larvae; the host continues life for a while, ignorant to the baby wasp that’s feasting on it from the inside out.
Gruesome? Maybe. Important? Definitely. Parasitoid wasps are of such importance in regulating insect populations that they are farmed on an industrial scale around the world to be released into huge crop fields to devour devastating crop pests. You encounter parasitoid wasps on a daily basis in the summer months – they are often tiny and insignificant. Take a closer look next time before squashing small black insects that look like skinny flies with long antennae.
Back to your picnic, where it’s time to talk about beer. Social wasps love beer – especially during the last throes of summer when you’re clinging desperately to the dregs of the holiday frenzy. Science explains this too. Although wasps are hunters, the adults are in fact strict vegetarians. For most of the year, adult social wasps are kept satisfied by the sugary rewards given to them by the larvae in return for the meaty meal they’ve just delivered. It is an unfortunate coincidence that larval snacks start to dry up about the time that you’re in full summer barbecue mode. This is because towards the end of the colony cycle in late August to early September, most social wasp larvae have pupated and don’t need feeding any more. This leaves several thousand worker wasps hungry. For more than 100m years they’ve solved this hunger gap by visiting flowers to feast on nectar, just like bees. In doing so, they also pollinate. Just like bees. In fact, in the absence of bees, social wasps can completely replace the pollination services that bees provide.
Some non-social wasps are specialist pollinators. Certain orchids have evolved to smell, look and feel like a female thynnid wasp and so male wasps swoon helplessly from orchid to orchid, victims of their own sexual drive with the only outcome being pollination. Fig wasps complete a cycle of birth, incest and death inside the fig fruit, and only newly mated females break out to carry pollen to another fig. Both plant and insect benefit, and their total dependency is one of nature’s most beautiful stories of coevolution. In stark contrast to those pollinating specialists, our social picnic wasp is as unfussy about flowers as she is about meat. Anything goes. This means that she may be an important backup pollinator in degraded habitats where no bee would dream of going.
Humans have made the wasps’ thirst for sugar a little easier to satisfy. Your beer or lemonade will serve as well as a flower substitute. Don’t blame the wasps – they’re just hungry.
I spend a lot of my summer apologising on behalf of wasps for the occasional sting. No one likes a sting (not even me), and they can be serious if they cause anaphylactic shock. But the same can be said for bee stings. People are more forgiving of bee stings, though, because of the misconception that bees are less likely to sting you than wasps as they die when they do so. In fact, the honeybee is the only species of bee that does die when it stings you. The 20,000 other species of bee don’t die and can keep on stinging you, just like a wasp.
At your barbecue, the wasp is out to get your sausage or your beer, not you. Unfortunately, you start behaving like an idiot when she arrives, flailing your arms around. To her, you resemble her greatest predator: the badger. Badgers bravely dig up whole wasp colonies, and stings are a tickle in their thick hide. If you don’t want to be stung, don’t behave like a badger. Stay still. Watch her. Work out what she’s after (I guarantee it’s not you), and offer her a share: a sliver of sausage, a saucer of beer. Edge this gradually away from your dining space, and wasp and human will both be happy. Or be like the Argentinians: put out a smelly bit of fish as a decoy, and the wasps won’t even notice your picnic.
Now you’re equipped with the science to understand why wasps do what they do, you can safely sit back and admire some of the natural world’s most beautiful, diverse, ecologically and economically important creatures. We can all learn to live well with wasps, as we have done with bees for millennia.
• Prof Seirian Sumner is a behavioural ecologist at University College London and the author of Endless Forms: The Secret World of Wasps
