THE WONDERFUL WASP
Wasps deserve respect not a swatter, says Seirian Sumner – who reveals their fascinating societies and hugely beneficial presence in our gardens and wider countryside.
Consider the sounds of high summer: the chattering of rooftop starlings, the hum of your neighbour’s lawnmower. Listen more closely and you might be hear the delicate scratching of a wasp on the wood of your garden shed.
Far from being a malicious pest looking to ruin your picnic, this lady (they’re all females at this time of year) is completely focused on collecting wood pulp to expand her mother’s nest. It’s a labour of genetic love – the harder she works, the more wasps her mother’s nest will produce, and the more of her genes will be passed on to the next generation.
The wasp in question is the yellowjacket (Vespula vulgaris), the black and stripy species you often find yourself swatting away. The reputation of this and a few other species has tarred that of another 200,000. Indeed, wasps are second only to beetles in terms of species numbers and there are thought to be at least 100,000 more waiting to be discovered. Social wasps (that includes our stripy friend) represent less than one per cent of the total wasp species in the world. And most aren’t yellow and stripy or fond of picnics. The vast majority of described wasps are tiny black insects that you’d probably mistake for flies. In fact, the smallest insect in the world is a wasp: the ‘fairyfly’ is a mere 0.14mm long and only lives for a few days. Despite its size, it plays a vital role in agriculture, as it lays its eggs in the bodies of crop pests, essentially working as an alternative to chemical pesticides.
There are many reasons to love (or at least appreciate) wasps, the main one being that they help keep insect, spider and woodlice populations at bay. As predators, they’re at the top of the food chain and without them food webs would break down. They’re also generalists: wasps will feed on whatever’s around. They eat the most abundant pests that we try to control with toxic chemicals – there’d be many more aphids in my garden without wasps. We don’t have good data on how much wasps eat, but a single colony is thought to remove somewhere
between 0.16-23kg of prey per season. Using a modest estimate, that amounts to about 250,000 aphids from each colony.
Wasps are also pollinators of flowers and crops. Adult wasps don’t need much protein (the bugs they prey on are for the developing brood in the nest) but they do need sugar, which they get in the form of nectar from flowers. In the process of finding it, the wasps pick up and transfer pollen from flower to flower. Unlike many bees, wasps don’t mind what flowers they visit – as generalist pollinators they’re more abundant than bees in degraded or fragmented habitats and so are important ‘back-up’ pollinators in these areas.
Wasps also have a fascinating social life. A yellowjacket colony is much like that of a honeybee, with a queen supported by a community of workers. It sounds harmonious but look closer and you’ll see a veritable Game of Thrones in full swing. The parallels with human societies are uncanny: there are specialist work forces, rebellions, policing, leadership contests, undertakers, police, even free-loaders and anti-social thugs. You name it, social wasps have it.
The lives of social wasps revolve around gene-sharing (or relatedness). Worker wasps are ‘self-sacrificers’, they have evolved to work rather than reproduce because their genes are passed on through the brood they help rear (their siblings).
But this social contract is only a good deal if their mother is singly mated. Queen wasps only have one mating flight in their lives, but during that time some species mate with several males: they store the sperm in their abdomen and control its release to fertilise the eggs they lay throughout their lives.
Multiple mating means the queen dilutes the relatedness of the workers in her brood and workers end up rearing a mix of half- and full-siblings, which can break the social contract of the colony. In these cases, workers can do better, individually, if they lay their own eggs. And this is when things get messy: sneaky egg laying by workers can cause a colony’s cohesion to break down, creating internal battles among the workers. They may be bloodless battles, as no insect blood (haemolymph) is shed, but they’re fought by ruthless means: workers that detect another worker’s eggs will eat them before they hatch.
But aren’t we taught in schools that only queens lay eggs? In fact, workers
“PERHAPS WE HAVE WASPS TO THANK FOR MUCH OF OUR RICH CULTURAL HISTORY”
in almost all Hymenoptera (bee, wasp and ant) colonies can lay eggs. Because of a genetic quirk of the Hymenoptera, females hatch from fertilised eggs and males from unfertilised eggs. Worker wasps have lost the ability to mate, but can still lay male (unfertilised) eggs.
GOOD FOR BODY AND MIND
There are other reasons to admire wasps. For one thing, they may be indirectly responsible for the invention of paper. Around 2,000 years ago a Chinese eunuch called Cai Lun noticed a wasp building a paper nest in his garden. Inspired by what he saw, he started to mulch wood and with it made the first paper. If the story is true, then perhaps we have wasps to thank for much of our rich cultural history and development.
Fast forward to today where exciting research is looking into the potential use of wasp venom as a cancer therapy. An active peptide found in the venom of tropical social wasps selectively destroys cancerous cells by causing their membranes to leak. Wasps may have the potential to save human lives.
A better appreciation of the ecological, economic, medical and cultural services that our stripy friends provide might help us see them in a different light. So next time your picnic is disturbed by black and yellow insects, take a moment to think about their extraordinary world and the contributions they make to our lives before you reach for the swatter.
WASP SURVEY You can take part in the 2018 survey by putting out a wasp trap between 25 August and the 1st September. Find full details of the survey at www.bigwaspsurvey.org
Dr Seirian Sumner is a behavioural ecologist at University College London. Her research focuses on understanding how and why animals and insects such as wasps live in societies.