What’s the point of wasps? This question emerges with tedious regularity whenever the yellow flash of a vespine forager ventures within a mile of a summer picnic or pub garden, often accompanied by idiotic assertions that wasps sting for no reason. Like much hostility and intolerance shown towards wildlife, widespread animosity to wasps betrays a lack of understanding or connection with nature.
What’s worse is that rather than informing and educating the public, the media often perpetuate these prejudices (nothing unusual there). One such article I came across recently, while presuming to advise readers about how to discourage wasps from gardens, displayed such ignorance that its main accompanying photo featured a hoverfly.
So, what is the point of wasps? Aside from the anthropocentric arrogance of the question, as if other species must justify their existence to us, it’s worth illuminating the diversity, importance and evolutionary ingenuity of these underappreciated insects, so that we might overcome our cultural aversion and focus on enjoying and conserving them.
Firstly, the term ‘wasp’ covers far more than the social yellowjackets with which we’re most familiar. There are tens of thousands of species of aculeate (stinging) wasps globally, most of which are solitary and relatively inconspicuous. There are additionally hundreds of thousands of species of (generally smaller) non-aculeate wasps. Of the several thousand species in the UK, fewer than 10 are large social wasps and hornets.
Most wasps are efficient predators or parasitoids of insects and arachnids, giving them an important regulatory function in controlling prey populations, including those of many crop pests. Social wasps are generalist predators, capturing various prey and taking it back to their nest to feed to the larvae. Others are more specialised: Ichneumonids, for instance, are solitary species that usually parasitise caterpillars. After mating, females locate suitable caterpillars and inject them with eggs, venom and symbiotic polydnaviruses that attack the caterpillar immune system. The wasp larvae then consume the caterpillar from the inside.
Many smaller non-aculeate wasps parasitise aphids, sneaking up and jabbing them with their ovipositor. Look closely at your runner beans in summer, and you may spot the dry, brown forms of ‘mummified’ aphids, which are the empty husks left after wasp larvae have pupated and emerged as adults from the aphid’s body. Some aphid parasitoids are so effective that they’re commercially sold as agricultural biocontrol agents.
Wasps are also important pollinators. Adults usually feed on nectar, visiting flowers opportunistically. Some are effective enough pollinators that they have been experimentally shown to maintain pollination of local plants at the same level after bumblebees are excluded, affirming their role in maintaining ecosystem resilience.
Some plants advertise specifically to wasps. Over 160 plant species across 6 families depend entirely on aculeate wasps for pollination and many, rather than a nectar reward, have evolved targeted and elaborate mechanisms of deception in order to maximise their attractiveness.
Some orchids mimic the physical appearance and sex pheromones of female wasps in order to attract males of the same species, inducing them to try to mate with the flower, whereupon pollinaria are transferred onto his body to be taken to another flower. Other orchids attract hunting wasps to pollinate them by mimicking leaf volatiles normally emitted by plants under attack from caterpillars, and some even attract hornets by mimicking alarm pheromones of their honeybee prey.
Perhaps the most intimate example of wasp pollination is the mutualistic relationship between figs and fig wasps. Figs are all pollinated by the Agaonidae family of wasps. What we call the fig fruit is actually a fleshy syconium enclosing hundreds of flowers. Female wasps carrying pollen enter these syconia through a small opening to lay eggs in the female flowers. As they move through the syconium they deposit pollen.
The larvae develop in the flowers where eggs were laid. Wingless males emerge first and begin searching for females. As the winged females emerge, the males mate with them, and then chew holes in the syconium through which the females escape, becoming dusted with pollen from male flowers before they leave. Thus, the wasps gain a safe site for reproduction, and the figs get pollinated. Because figs flower all year round, they offer a reliable food resource for a range of birds and mammals, largely thanks to fig wasps.
Less well known to date is the prevalence of ‘vespicochory,’ or seed dispersal by wasps. This works on a similar basis to the better documented seed dispersal by ants – the insects are attracted to fatty tissue (elaiosome) surrounding seeds. They carry the seeds away before chewing off this elaiosome and discarding the intact seed. Vespicochory has been observed in several ecosystems, and for at least one East Asian plant, social wasps are the primary seed dispersers. Because they forage by flight, wasps carry seeds over greater distances than ants, typically over 100m from the parent plant.
Even the feature that gives wasps a bad name – the sting – may hold benefits for humanity. Wasp venom is a cocktail of various peptides and aromatic compounds, some of which have potential for treating various types of cancer.
This barely scratches the surface of the diversity and ecosystem services that make wasps an invaluable and impressive part of insect communities. It’s a gross injustice that we rightly revere bees, while vilifying wasps – after all, bees are merely wasps that went vegetarian around 100 million years ago. One may not want a common wasp nest in one’s loft, but we should care just as much about their preservation as we do about bees, butterflies or beetles.
With that in mind, keen UK citizen scientists could sign up to participate in the annual Big Wasp Survey (BWS) in the summer to learn more about our common social wasps. If you have access to outdoor space and don’t mind sacrificing half a can of lager, you can construct a simple trap to collect wasps for identification, and contribute to the population data that the survey hopes to gather.
The BWS has already generated valuable information over a relatively short period. As pointed out by Professor Seirian Sumner, an evolutionary biologist researching social insects at UCL, author of the recent book Endless Forms: Why We Should Love Wasps, and a coordinator of the BWS, ‘2023 will be the seventh year of the Big Wasp Survey. The last seven years of data have revealed the diversity and distributions of social wasps across the UK, and how populations vary with different types of habitat. The secret to the social wasps’ successes in the UK is their resilience to urbanisation and their ability to disperse far and wide.’
Additionally, gardeners should stop using pesticides; wasps help to control pests anyway, and insecticides are often counterproductive precisely because they harm insect predators as much as the pests they hunt. Instead of discouraging wasps from your garden, grow flowering plants to attract them. With biodiversity in freefall the world over, we can no longer afford such intolerance. If we can rectify our attitudes towards wasps, there may be hope for the rest of our wildlife.
Related: Finding Humanity in Travesty
