EVERYBODY loves bees. They are celebrated for their glorious honey, cooperative work ethic and commercially valuable pollination services. In a 2019 survey, 55 per cent of respondents chose bees as the species they most wanted to save, above the likes of elephants and tigers.
. These most unwelcome picnic guests have been reviled for millennia. Ancient Greek essayist Plutarch described wasps as degenerate bees. The very word “waspish” summons up ideas of irritability, implying they are quick to anger, spiteful and vindictive. And that’s just the regular wasp or yellow jacket. Our attitudes to the largest wasp species, hornets, are even more negative. The tabloids hawk horror stories about how the , Vespa velutina, threatens honey production and native pollinators in the UK. Meanwhile, persecution of the huge but docile European hornet, Vespa crabro, continues, fuelled by fear and ignorance, even though its numbers are declining. Few people seem to care.
But are we judging this diverse group of insects unfairly? Certainly, our perceptions are ill-informed. There are whole institutes dedicated to studying bees, while wasp research is in the doldrums. Limited funds attract few projects, the results of which are often misconstrued in the press, bolstering an already negative stereotype. In fact, what we have learned about wasps tells a different story. Far from being bothersome and vindictive, they make valuable contributions to ecosystems, the economy and even our health.
Advertisement
Take ecosystem services – a buzz phrase of our time that means the quantifiable benefits nature provides for us. Honeybees may be the prime pollinators of many cultivated fruit crops, but wasps and other insects pollinate most wild flowers. Indeed, . Among them are almost 100 species of orchids, including helleborines. These widespread but scarce plants of woodland edges have a cunning trick to entice pollinators. Their flowers produce the sort of volatile chemicals that other plants emit when under attack from caterpillars, which lure . The wasps then sip the nectar in the orchid flowers, which contains soporific agents – – that slow them down, increasing the likelihood they will pick up pollen. Without their tipsy wasp pollinators, these elegant plants would become extinct.
Ěý
Pest control
Wasps also benefit us even more directly. They are the third most important predators of insects after birds and spiders. They use their powerful triangular jaws to kill prey, snatched from plants or from mid-air. Once the victim’s nutrient-poor wings are scissored off, the dismembered bodies are taken away to feed to the ravenous brood back in the nest. A mature wasp colony is reckoned to take between 3000 and 4000 prey a day at the height of the season. By one estimate, in the UK alone, .
They target woodlice, spiders, flying beetles and, less endearingly, butterflies and honeybees. But they also make quick work of many serious crop pests, including aphids, caterpillars, plant bugs and flies. There have long been anecdotal reports of plagues of flies on private estates after overzealous wasp nest clearances. In the early 20th century, small, umbrella-shaped nests of paper wasps were placed around Caribbean cotton fields to control infestations of voracious moth caterpillars called cotton bollworms. Likewise, in the sugar cane fields of the Philippines, paper wasps were used to help suppress sap-sucking planthoppers. Recent research reveals that another paper wasp, the provocatively named of two of the world’s most rapacious pests, the sugar cane borer and the fall armyworm, which eats crops including maize.
Even the sting in a wasp’s tail has potential to help us. Wasp venom evolved to kill prey, but social species also use it for defence. Their succulent, protein-rich grubs are a favourite of the misnamed honey badger and honey buzzard, among other animals. Subterranean nests are their preferred targets and, to protect themselves while digging out wasp grubs, honey badgers have dense shaving-brush bristles on their snouts while honey buzzards have small, dense guard feathers around their faces. As the defences of predators have evolved, so too has the potency of wasp venom to keep them at bay.
Partly as a result of this evolutionary arms race, a wasp sting is a potent weapon. On average, a sting delivers 15 microlitres of venom – a complex cocktail of bioactive molecules that varies from species to species. It includes histamines to increase blood flow, proteases and lipases to rupture flesh and blood cells, and neurotransmitters to confuse and overstimulate nerves. Humans may not be the intended target, but a single wasp sting can raise a welt the size of half a ping-pong ball. Multiple stings can cause redness, nausea, vomiting, wheezing and confusion. If you receive over 100 of them, you should seek emergency medical help: there is no antivenom, but from the blood before significant organ damage occurs. The average adult would be lucky to survive 1000 or more wasp stings.
Paradoxically, however, venoms often have medical applications. Although little research has been done on wasp venom, it is likely to be no exception, if bee venom is anything to go by. There is a long tradition of beekeepers accidentally (and deliberately) courting bee stings to get relief from the pain of rheumatoid arthritis. Tests in animals confirm that . This may work by stimulating the immune system or increasing the release of corticosteroids, which quell inflammation.
Therapeutic venom
Being more varied than bee venom, wasp stings may prove even more useful as a source of medicines. Several active ingredients already show promise. An extract of the venom of the large, black Brazilian wasp, Polybia paulista, for example, (in mice, at least) by attaching to particular lipid molecules in their membranes. This extract is one of a class of wasp venom components called mastoparans.
. It latches on to specific lipids too, so could be used to rupture cell membranes in targeted body tissues, either to destroy cells or to create portals for pharmaceuticals to get into them. It also shows encouraging antibacterial and antiviral qualities, and inhibits the development of the parasite that causes Chagas’ disease. Further wasp venom constituents are being explored as , allergies and cardiovascular disease.
“Some orchids would become extinct without their tipsy wasp pollinators”
As if all this weren’t enough, wasps can play a role in conservation too. They are affected by climate change, intensive agricultural practices and the same pesticides that are implicated in a widespread decline in insect numbers. All this makes them good indicators of environmental stress, if we can track their fate. In 2017, the was launched in the UK to do just that. It is a citizen science project that aims to map the diversity and location of wasps by sampling specimens using traps in gardens all over the country and comparing year-on-year numbers of species and individuals.
Our ignorance about wasps is still vast but, by looking beyond our prejudices, we can see their potential to tackle some of the biggest problems we face. A wider understanding of their diversity (see “What is a wasp?”), life histories, ecologies and behaviours is long overdue. It is time we stopped demonising wasps and learned to love them.
“With a quarter the number of species, you might say that bees are just specialised, vegan wasps”
What is a wasp?
Say “wasp” and most people think of social wasps of the family Vespidae, often called yellow jackets in North America. These relatively large, mostly black-and-yellow species live in colonies of between 50 and 10,000 individuals and inhabit nests of paper-like material made from chewed wood pulp. Yet they comprise less than 4 per cent of more than 110,000 known wasp species.
And less than a third of wasp species have evolved what we tend to think of as the defining wasp characteristic: that painful sting. Stinging species are predatory, whereas the remainder are parasitic. And the vast majority of wasp species are solitary, often living secretive lives that are easily overlooked.
Wasps come in myriad varieties. Pale, flimsy fairy wasps parasitise insect eggs. As little as 0.14 millimetres long, they are possibly the smallest insects. Ant-like gall wasps have chemicals in their stings that induce bizarre growths called galls on plants. Their offspring then develop within these structures, which include ball-like oak apples on oak trees and moss-like robin’s pin-cushions on some shrubs. Spider-hunting wasps stock a burrow with paralysed but living arachnids on which their larvae then feed. Potter wasps make nests of mud. Mason wasps burrow into loose mortar. And ichneumon wasps lay their eggs inside moth caterpillars.
Whatever form they take, wasps – along with bees, ants and a whole host of other svelte, narrow-waisted insects – belong to the order Hymenoptera, from the Greek meaning membrane-winged. These insects have four wings, a larger front pair and a smaller back pair latched together by a row of microscopic hooks (the hamulus) to make a more efficient single aerofoil. However, they don’t adhere to the conventional three-part insect body plan of head, thorax and abdomen. Instead, the first segment of the abdomen is fused to the thorax to create a compound body called the mesosoma. Then there is a narrow, stalk-like waist between the mesosoma and the rest of the abdomen. This acts like a universal hinge, allowing the posterior section to be pointed in almost any direction, which is particularly useful for species with a sting in the tail.
Vespidae wasps shared a common ancestor with bees some 175 million to 200 million years ago. The main difference between them is that bees feed exclusively on nectar and pollen, whereas wasps have more wide-ranging tastes. Adults may visit flowers to take the odd sip of nectar for energy, but small insects are the main source of food for wasps and their larvae, and they aren’t above dining on carrion and ripe animal scats. With bee species numbering a mere 25,000, you might even say that they are just specialised, vegan wasps.
Article amended on 30 March 2020
We corrected our illustration of a pollinating wasp.
