It is unknown how many species of wasp there are in the world, but it is likely to be about 75,000. Most lead solitary lives and rely upon venom in their sting to immobilize prey. However, some live in large colonies.
Most species of wasps are solitary, living alone. However, wasp nests can often be found hanging in voids and cavities of homes, garages, and under trees. One female, the Queen lives in the nest and can be surrounded by up to 3,000 workers.
If you want to know more about the social structure of wasps, please read on.
Wasps, along with bees, ants, sawflies, and other parasitic insects, belong to the order Hymenoptera. Except for sawflies, they all have a very narrow connection between their abdomen and thorax, known as a wasp-waist.
Many hymenopterans are commonly called wasps but are not true wasps such as ichneumon. True wasps are characterized by two features—their ovipositor is modified to form a sting, and they feed the adult captured prey, such as insects or spiders. The adult true wasps are usually black and yellow or black and red and feed upon nectar.
As a group, the wasps show a remarkable variety of lifestyles, each evolved to maximize the survival of their species. Each species of wasp specializes in certain kinds of prey, often flies and beetles. The stings of these wasps inject a venom that paralyzes insect prey but has little effect on vertebrates.
True wasps can be split into two broad categories: the solitary wasps, which make a dozen nest cells in a season, and social wasps, which are highly organized with a queen, workers, and a large nest containing thousands of cells.
Solitary wasps
Wasps seek out their prey, often in soil, then immobilize it with a sting before laying an egg on it. In this way, they show a close resemblance to the parasitic ichneumon wasps. All other solitary wasps find their prey, sting it and then transfer it to a nest where it is stored in a live, paralyzed state for the young grubs to feed on.
Prey is carried back to the nest in a variety of ways. The wasp often grasps a leg in its jaws and drags the prey backward. All other wasps use their legs in one way or another to hold the prey beneath their bodies as they fly or walk. Social wasps tend to hold their prey in their jaws and front legs, while some solitary wasps fly with prey impaled on their stingers.
Adult wasps use nectar as a source of energy and do not eat their prey. But it is not uncommon for them to chew at their prey and drink their body juices. Some species that attack bees often drink the contents of the bees’ stomachs.
In common with social wasps, solitary wasps lay their eggs in constructed cells. In the case of solitary wasps, these cells are built inside shafts usually dug in soil, though a few species prefer to use holes in wood or walls. Once the shaft has been dug, the mother wasp begins to lay her eggs inside the cells. In the innermost cells at the back, she lays fertilized eggs that will hatch into females, while at the front of the shaft, unfertilised, male-producing eggs are laid.
It is not known how the mother knows whether to lay fertilized or unfertilized eggs. The separation of the sexes is to encourage males to emerge early in the following year, and it also helps to prevent mating between brother and sister.
As the mother wasp lays her egg in each cell, she adds prey items to provide food for the emerging grubs. Male grubs receive less food than females since the females will grow to become larger.
In practically all solitary wasps, the mother wasp never sees her offspring, as she dies at the onset of autumn while the now mature grubs pass the winter safe inside their cells.
Parasitic Wasps
Wasps most closely related to the ichneumons include Tiphia— black wasps which burrow into the soil in search of larvae of chafer beetles on which they lay their eggs. The beetle larva usually recovers after the sting and continues feeding until it eventually succumbs to the feeding of the Tiphia larva.
The wingless females of the wasp Methoca ichneumonoides specialize in attacking the larvae of the tiger beetle in their burrows. The wasp locates the tiger beetle burrow and immobilizes the larva with a sting before laying an egg on it. Once the wasp has immobilized the beetle larva and laid an egg, it fills the burrow with soil.
All other solitary wasps prepare a nest for their prey, either before or after catching and stinging it. The spider hunting wasps catch a spider before dragging it to a suitable site for excavating a burrow while other species dig it first and then seek prey to fill it. These species have to memorize the exact position of their burrows and use bushes, stones, and debris on the ground as clues to relocating them.
Species of Cerceris burrow with their legs and eject soil with their tail acting as a ram. There are two common species of Cerceris; one catches weevils, and the other prey on bees. They furnish each cell with several items of prey before an egg is laid and the next cell started.
The position of the egg is important because the young grub must be able to find food straight away. With hard-bodied weevils, the egg is usually placed in a soft part such as where the leg joins the body.
Wasps of the genus Crabro often make their nests in decaying wood, each nest consisting of a row of individual cells stocked with flies.
The red and black sand wasp, Ammophila pubescens, differs from other solitary wasps in that the female does not stock the cells and leave them but maintains two or three single-celled nests in the sand at the same time.
She places an immobilized caterpillar in each cell and lays an egg on it before putting a temporary closure of small pebbles over the cell entrance. Every day she removes the plug and inspects each cell to decide whether the larva needs more food and, if necessary, she fetches another caterpillar. The cell is only sealed over permanently once the female wasp is satisfied that the larvae are fully grown.
Wasp Nests
Potter and mason wasps are closely related to the social species and are known for building a small nest of clay or mud. The female mason wasp, such as Ancistrocerus, finds a suitable hole in a wall or wood, where she makes several cells. Each cell is separated from its neighbor by a mud partition and has an egg laid in it before being filled with a dozen paralyzed caterpillars.
The female potter wasp, Eumenes coarctatus, makes a flask-shaped nest from mud pellets on low bushes such as heather. She lays her egg before storing up to 20 small paralyzed caterpillars and sealing the neck of the nest with more mud.
The larvae feed quickly and, as with other solitary wasps, remain as fully grown larvae through winter to pupate in the spring.
Queen
The queen emerges from hibernation in spring and seeks a suitable site in which to build a new nest. The nest is made from chewed wood fragments fashioned to form a globe, inside which combs of cells are suspended.
In each cell the queen lays a single egg, and when the eggs hatch, she supplies them with food in the form of insects such as flies. The grubs grow over the next few weeks, pupate and then hatch as adult wasps. These wasps are the subordinate workers that take over the chores of the queen and leave her free to stay in the nest and lay more eggs. Each worker lives for about three weeks, and at the height of the season, a nest may contain around 3000 workers.
As with honey bees, there is a constant exchange of food among the individual wasps, and this activity ensures that the queen is fed. These exchanges seem to contribute to discipline in the colony and regulate the behavior of the wasps. This is also helped by the queen’s presence, without whom the colony would lose coherence and eventually disintegrate entirely. This naturally occurs in autumn when the old queen dies after rearing new queens for the following year.