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Rosie Wirsing
There are over 7,000 wasp species living in the UK, comprising a huge variety of solitary and social species. The majority are parasitoids, which have young that eat insects or spiders alive. However, the most commonly seen wasps are the black and yellow social species.
Colonies of social wasps are considered annoying pests - they often nest in manmade structures and deal out painful stings if you get too close. Yet despite our grievances, the ecosystem actually relies on these underappreciated insects.
Without wasps, the world could be overrun with spiders and insects. Each summer, social wasps in the UK capture an estimated 14 million kilogrammes of insect prey, such as caterpillars and greenfly. Perhaps we should be calling them a gardener's friend.
Wasps are hugely beneficial to their native ecosystems due to the sheer amount of insects they capture. But their voracious appetites can cause problems if a species spreads or is introduced to new areas and their numbers aren't kept under control, such as in New Zealand, where there are no native social wasps.
'Where common and German wasps have been accidentally introduced to New Zealand, they've been stripping caterpillars out of forests. This is having a huge ecosystem impact and the native birds have been declining.'
Some solitary species are more sinister. For example, most spider wasps paralyse arachnid prey using a venomous sting. Their larvae then eat the victim alive. There are almost 5,000 species of spider wasp worldwide, including 44 species in Britain.
Instead of eating insects and spiders, adult wasps - both social and solitary - only feed on sugars. In the wild, sugars come from flower nectar and honeydew produced by aphids. Wasp larvae also produce a sugary liquid that the adults consume.
When on the hunt for nectar, wasps can also become accidental pollinators by travelling from plant to plant carrying pollen. While their contribution to pollination may not be as substantial as bees', wasps still play a valuable part.
Wasps are also a food source for other animals - including other wasps. In this image a European hornet (Vespa crabro) has captured a smaller social wasp, most likely a German wasp (Vespula germanica), which will then be chopped up and fed to the hornet's own larvae. Dimitǎr Boevski via Wikimedia Commons (CC BY-SA 4.0)
Ancestors of the wasps most commonly found in the UK nested in cavities. This has resulted in species that thrive in manmade structures such as sheds and lofts. This sometimes makes wasps a pest problem when the colony mass increases.
The European hornet is the UK's only native hornet species and is the largest of our social wasps. Their bodies are also yellow with a dark pattern - although it has a sting that is more painful than other social wasps in Britain, usually leaving the stung area throbbing for a few hours.
The European hornet (Vespa crabro) shares a similar colouration and pattern with a number of other social wasps. This is a form of Müllerian mimicry. Jerzy Strzelecki via Wikimedia Commons (CC BY-SA 3.0)
Although wasps may cause us strife in the summer months - and leave some to question the point of them - these insects play a crucial role in maintaining harmony in the ecosystem. We certainly would not be able to cope in a world without them.
All wasps build nests. Whereas bees secrete a waxy substance to construct their nests, wasps create their familiar papery abodes from wood fibers scraped with their hard mandibles and chewed into a pulp.
Solitary wasps, by far the largest subgroup, do not form colonies. This group includes some of the wasp family's largest members, like cicada killers and the striking blue-and-orange tarantula hawks, which can both reach 1.5 inches in length. Whereas social wasps use their stingers only for defense, stinging solitary wasps rely on their venom to hunt.
Most animals have developed a well-earned fear of stinging wasps and give them a wide berth. Creatures who haplessly stumble upon a wasp colony or have the audacity to disturb a nest will find themselves quickly swarmed. A social wasp in distress emits a pheromone that sends nearby colony members into a defensive, stinging frenzy. Unlike bees, wasps can sting repeatedly. Only females have stingers, which are actually modified egg-laying organs.
Despite the fear they sometimes evoke, wasps are extremely beneficial to humans. Nearly every pest insect on Earth is preyed upon by a wasp species, either for food or as a host for its parasitic larvae. Wasps are so adept at controlling pest populations that the agriculture industry now regularly deploys them to protect crops.
Social wasps are a group of related insects belonging primarily to the family Vespidae (sometimes called vespid wasps). Being social means many individuals share one nest. Solitary wasps and bees nest alone. This article focuses on the habits of social wasps and bees.
All wasps and bees have a complete life cycle with egg, larval, pupal and adult stages. We generally see only the adults as the eggs and larvae are in the nests. The larvae of bees and wasps are white and typically look like grubs.
Yellow jackets, paper wasps and bumble bees can sting more than once because they can pull out their stinger without injuring themselves. If you are stung by one of these insects, the stinger is not left in your skin.
Yellowjackets and other social wasps are found in large numbers in late summer and fall. The wasps are present since spring, but because colonies start as a single queen, populations are very small through the early part of the summer.
Yellowjacket populations peak during late summer when each nest may have up to approximately 5,000 wasps. Some yellowjacket species become aggressive scavengers and can disrupt outside activities where food or drink are served.
Results: We have precisely mapped the sensory neurons that are used by the Drosophila larvae to detect nociceptive stimuli. By using complementary optogenetic activation and targeted silencing of sensory neurons, we have demonstrated that a single class of neuron (class IV multidendritic neuron) is sufficient and necessary for triggering the unusual rolling behavior. In addition, we find that larvae have an innately encoded preference in the directionality of rolling. Surprisingly, the initial direction of rolling locomotion is toward the side of the body that has been stimulated. We propose that directional rolling might provide a selective advantage in escape from parasitoid wasps that are ubiquitously present in the natural environment of Drosophila. Consistent with this hypothesis, we have documented that larvae can escape the attack of Leptopilina boulardi parasitoid wasps by rolling, occasionally flipping the attacker onto its back.
As stated earlier, the vast majority of wasps are carnivorous. However, these wasps cannot survive based on a completely meat-diet; they in fact need to supplement their diets with sugar and water, which very often comes from flower nectar, or honeydew produced by insect herbivores (e.g., aphids). Similar to bees, wasps have high energy requirements, and pollen and nectar allow them to acquire extra energy to use for their high metabolisms. For this same reason, it is not uncommon to observe wasps feeding on fruits (e.g., apples, pears, grapes and blackberries; Fig. 3), fruit juices, honey, jam and pies.
Some wasps, such as yellow jackets, have diverse diets and can consume some of the same foods that humans eat, which is why we often find them swarming our picnic plates and garbage cans. Carnivorous wasps are hunters, and prey on other insects and arthropods, including herbivores that feed on important crops. True wasps have stingers and use them to capture insects or spiders as food for their larvae. Other wasps are parasitic and use their ovipositors to lay eggs on or in the bodies or eggs of other insects, which then become their hosts. In those cases, the immature wasp or developing larva develops inside the host while feeding on its tissues. Many species of parasitic wasps use hosts as direct food or for oviposition. Some female parasitoids feed from and oviposit eggs on the same host individual, while females of other species may use a host solely for food or oviposition. When host feeding occurs, females are believed to obtain nutrients that can be used to produce more eggs, and to enable further host searches.
Pollen wasps are unique among wasps, not only because of their diets, but also because of their behavior. In fact, many of their characteristics resemble bees. For instance, like most bees, they are solitary and have long mouthparts, which allows them to reach the nectar of flowers with narrow and deep corolla tubes such as beardtongues (Penstemon). However, unlike many bees who display a corbicula (pollen basket) on their hind legs to transport pollen, pollen wasps collect pollen in their crop (expanded portion of their digestive track that can be used to temporarily store pollen and nectar). Like many bees and wasps, it is the females who are responsible for building the nest, which is hard, made of mud and cemented with secretions from their salivary glands. Nests are usually built in concealed places such as under rocks and crevices, although they may be attached to rocks, ledges, and tree twigs. Similar to many bees, each cell in the nest contains a single pollen-nectar loaf on which an egg is laid, and is sealed with a mud plug. Pollen wasps are known to specialize in foraging on very specific flowers, including beardtongues, borage and tansies, in which they play an important role as pollinators. For instance, a number of rare beardtongue species rely on Pseudomasaris vespoides pollination, giving the insect an important role in maintaining ecological diversity.
Adult wasps only feed on sugars, which they may obtain by feeding on nectar, honeydew from insects such as aphids, and fruits. However, most wasp species hunt other invertebrates to feed their offspring. Thus, adult wasps do not eat the prey they hunt as they feed it to their young. Despite the fear they sometimes evoke, wasps are extremely beneficial to humans. While searching for nectar, wasps become accidental pollinators, carrying pollen while they travel from plant to plant. However, wasps also serve humans by helping regulate insect pest populations. Relative to this, nearly every insect pest on Earth is preyed upon by a wasp species, either for food or as a host for its larvae. Wasps are so adept at controlling pest populations that the agriculture industry now regularly deploys them to protect crops. A study conducted in Brazil found that social wasps are effective predators that can manage pests in maize and sugarcane. To this point, predatory and parasitic wasps are very valuable natural control agents that help to control insect pest populations in multiple cropping systems. A caveat to this is that one must consider that predatory wasps are generalist predators and, as such, may hunt other beneficial insects such as pollinators, parasitoids, and other predators that may also help control insect pest populations (Fig. 8).
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