Wasps are generally thought of as pests, but in fact they are great garden helpers. Here’s the Royal Entomological Society’s guide to wasps in the garden
During the summer months it can seem wasps’ main role is to disrupt family picnics but these important, incredibly well-adapted, and largely harmless to humans, predators are an incredible asset to gardens. Prof. Seirian Sumner FRES, a British entomologist and behavioural ecologist at University College London, an expert in social wasps and a Trustee of the Royal Entomological Society and Fran Sconce, entomologist and Royal Entomological Society Outreach Officer joins us to help change gardeners’ minds.
There are over 100,000 species of wasps currently described in the world, and in the UK alone there are 7,000 species. Social wasps – yellowjackets and hornets, which are the ones that most people recognise as wasps – account for only around 1,200 of total known species – and for only 9 in the UK. Most people don’t like wasps because they sting, however it’s worth remembering that bees sting too, and yet gardeners love bees because of their pollination services and a long-held view that bees are ‘useful’. Yet wasps not only provide similar pollination services, but they are also a natural form of pest-control and are very efficient decomposers making them extremely ‘useful’ garden companions.
The vast majority (around 70 per cent) of wasps don’t sting
Wasps can be found everywhere: some species have been able to adapt their lifestyles to make use of human-modified landscapes, for example social wasps often make their nests in lofts and sheds; others require very specific habitats, for example solitary digger wasps and potter wasps require heathland. Gardens provide particularly good habitats for wasps, especially if there’s lots of dead wood, exposed soil, flowers, water and a healthy population of other insects.
Parasitoid wasps detect hidden caterpillars or other insect larvae, lay their eggs in/on them, and then abandon their offspring. The hatched larva then feasts on the prey, as it goes on living.
Wasps are hunters, usually of other insects and arthropods, because their offspring require meat to develop into adults. This makes them very efficient natural pest-controllers, including insect pests in gardens like caterpillars, aphids and weevils. Wasps are also pollinators. Adult wasps may be hunters, but they don’t eat the meat themselves. They find nutrition from nectar in flowers and in doing so, they carry pollen from flower to flower. Social wasps are also decomposers. They hunt carrion, as well as fresh prey, and so are important in gardens in clearing up dead creatures – including your leftover BBQ sausage…
The vast majority (around 70 per cent) of wasps don’t sting – they have an ovipositor (an egglaying sheath) that they use to lay an egg on or in their prey. These are known as parasitoid wasps; they detect hidden caterpillars or other insect larvae, lay their eggs in/on them, and then abandon their offspring. The hatched larva then feasts on the prey, as it goes on living. To do this effectively, the parasitoid mother injects venom into her prey to suppress its immune system.
Wasps not only provide similar pollination services to bees, but they are also a natural form of pest-control and are very efficient decomposers making them extremely ‘useful’ garden companions
The remaining species of wasps do have stings. They include the solitary hunting wasps (around 30 thousand species worldwide). These tend to hunt a specific type of prey, depending on the species, for example the spider hunting wasps hunt only spiders; whilst other types of solitary wasps will only hunt caterpillars, weevils or flies. They paralyse their prey and bury it in the ground to lay an egg in/on it which, when hatched, will feast on the paralysed prey.
Social wasps only become bothersome at the end of the summer. This is when they have less hunting to do as most larvae have pupated (and don’t need feeding).
The social wasps (those that live in colonies) catch live and dead prey and bring it back to their colony to feed to developing larvae. Their societies are just like those of honeybees: a single queen lays the eggs, which are cared for by thousands of workers. It is the workers that do the hunting and feeding and in return, the larvae give the workers a sugar reward each time they are fed, providing the adult wasp with some nutrition. The colony produces only workers until the late summer, when the queen switches to producing sexual brood – young queens and males. Males die after mating (with new queens from other nests), along with any remaining workers and the old queen. Mated young queens hibernate and establish a new nest next spring.
Put out a ‘wasp offering’ like some jam or other sugary treat, a few metres away from your dining area, and the wasps will be happy and stay away from you
Solitary wasps won’t bother you at all – you won’t even know they are there. Social wasps only become bothersome at the end of the summer. This is when they have less hunting to do as most larvae have pupated (and don’t need feeding). The wasps are still needing food themselves though, and this is when they start to bother us at picnics. Put out a ‘wasp offering’ like some jam or other sugary treat, a few metres away from your dining area, and the wasps will be happy and stay away from you.
Resist the urge to call in the pest controllers as soon as you discover a wasp nest in your garden. Remember the good things wasps are doing for you: can you live for another few weeks with these helpful insects? If so, then they will produce the sexuals (young queens and males) that will be the pest controllers and pollinators for you next year and for many years to come.
Did you know the Royal Entomological Society offers an insect identification service? If you would like to know more about an insect you have discovered in your garden, you can fill out the form on the RES website here and one of the RES team will contact you with more information.
FACT FILE
• The Giant Northern hornet, Vespa mandarinia, has a wingspan of 12 cm and can fly up to 40km/hr. Scary though it sounds, in its native Asia, people farm these wasps for their tasty and nutritious larvae.
• The smallest wasp is the fairy fly, but it’s actually a parasitoid wasp – less than 0.015mm in size, it lives for only a few days but is an important pest controller.
• There are twice as many described species of wasps (100k) in the world than all the known bees (22k) and ants (18k) combined. And there are probably 5 times more wasp species yet to be discovered.
For more in depth reading about wasps: Endless Forms: Why you should love wasps by Prof. Seirian Sumner (William Collins).
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