August is wasp season, when people get up close with Vespula vulgaris, the common wasp. Vespa, meaning wasp in Italian, is a name shared with the fashionable moped with its high-pitched engine buzz reminiscent of the insect.
Wasps, unlike the eponymous moped, are not fashionable or desirable. Seirian Sumner’s book Endless Forms aims to change the public perception of wasps. While they may never reach the heights of popularity of their vegetarian bee cousins, there is plenty to be fascinated by.
The familiar yellow and black bane of late summer barbecues and picnics is just one of an estimated 100,000 named species of wasps, with hundreds of thousands more species as yet unnoticed and undescribed.
Part of the reason for this hidden diversity is that the majority of wasps live as parasitoids, inside other insects. Juvenile parasitoid wasps develop from eggs laid inside other insects and to complete this Russian doll arrangement there are even hyperparasitoid wasps that live inside the parasitoids inside other insects.
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The adult wasps must detect and lay eggs in the right kind of insect using their long ovipositor, which in the common wasp is an organ modified into the familiar stinger to deliver venom and not eggs. Given the many species of beetles and other insect hosts, it is not surprising that parasitoid wasp diversity is explosively rich. There are probably more species of wasps on this planet than any other animal group.
The common wasp is a predator, with the adults hunting for caterpillars and other insect larvae. Common wasps, like bees, are social with the queen setting up a colony in spring by building a nest from chewed wood fibres, laying the first batch of worker eggs and feeding the developing larvae with prey and fluids.
As the colony grows the queen loses the ability to fly and dedicates herself to producing eggs, up to 200 per day. The workers are now responsible for the success of the colony, providing food, cleaning it, moderating the temperature and defending against attack.
Next time you come across a wasp at a picnic remember it is at the endgame of its short life, spending its final days partying
Workers cannot eat the food they forage for themselves because of the tight “wasp waist” between their thorax and abdomen. Instead, they chew up the caterpillars and feed them to the developing wasp larvae, with the larvae producing a sugar rich secretion which they feed back to the adult workers. And here lies the origin of the summer “wasp problem”.
Late in the summer the queen dies and the colony starts to fall apart. The workers no longer have access to the sugar-producing larvae and have to find their sugar fix elsewhere. Over-ripe, rotting and fermenting fruit, often containing alcohol, becomes their “go to” diet, but wasps have also extended their diet into sugar-rich picnic foods and bottles of beer. The sugar and alcohol crazed workers then become persistent and irritating.
The boorish behaviour of the common wasp gives the hundreds of thousands of other wasp species a bad name. Wasps are important for the control of insect pests by ingesting leaf-munching caterpillars and creating zombies out of beetles and spiders. Solitary wasps, unlike their social cousins, work alone. They inject an anaesthetising sting into their prey to immobilise it but keep it alive as a larder for their larvae to feast on. The zombie prey are dragged to the nest or burrow where an egg is laid and the developing larva eats the zombie alive.
Living prey are less likely to get infected with bacteria and fungi and therefore provide a safe meal for the youngsters. Wasp mothers are very hygienic and some cover their nest and food sources with antibacterial and antifungal saliva, a potentially important source of human antibiotics.
Next time you come across a wasp at a picnic remember it is at the endgame of its short life, spending its final days partying. The unwanted guest is just the tip of the wasp diversity iceberg, with cousins who can be solitary or social, yellow and black striped, jewel coloured, minute Russian dolls or terrifyingly large tarantula spider hunting zombie-makers.
Yvonne Buckley is an ecologist and professor of zoology at Trinity College Dublin