Wasps and bees, together with ants, belong to a group of insects called the Order Hymenoptera. This is one of the largest insect groups. There may be as many as 44 000 Australian species of Hymenoptera, most of them wasps and bees.
Wasps and bees have bad reputation because of the aggressive nature and painful stings of a few species. In fact, there is no other group of insects that is more beneficial to humans. Most wasps are parasites or predators of other insects, including many pest species, helping control their numbers. There are many examples of exotic pest insects being successfully controlled by introducing their wasp parasites from overseas.
Bees are vitally important for pollinating plants, including many orchard trees, vegetables and crops that we rely on for food. Some flower wasps pollinate orchids and the world’s many species of fig trees are pollinated by minute fig wasps. The honeybee also produces honey in commercial quantities.
Wasps and bees encompass a far greater variety of insects than most people realise. They include the vegetarian sawflies, the most primitive of wasps. The vast majority of wasps are parasites including many that are minute. Honeybees are familiar to most, but few people know about our native stingless bees that also live in hives. Even less well-known is that the vast majority of Australian bees don’t live in hives but are solitary, each female making her own nest.
A sawfly, Pterygophorus insignis, whose caterpillar-like larvae feed on Paperbark leaves.
A parasitic ichneumon wasp, Netelia sp. These wasps lay eggs inside moth caterpillars. The eggs hatch and the wasp larvae consume the caterpillar from the inside.
A cuckoo wasp, so called because they lay their eggs inside the nests of other wasps. The cuckoo wasp larva either consumes the larva of the host wasp or its food supply.
A digger wasp, Sphex cognatus. The nest of this wasp is a burrow in the soil with several chambers. A single larva develops in each chamber feeding on katydid grasshoppers collected by the female.
Most wasps and bees have two pairs of gauzy, usually transparent wings that have only a few veins. The forewings are larger than the hindwings. In flight the forewing and hindwing are held together by a row of tiny hooks. Some wasps, such as flower wasps and velvet ants, have wingless females that resemble ants. They can be distinguished by their antennae which are not elbowed like those of ants.
The most primitive group of wasps are sawflies. These are thickset wasps that have no narrow waist. The larvae of many sawflies resemble caterpillars and have three pairs of jointed legs on the thorax. All other adult wasps, bees and ants, have a narrow waist at the base of the abdomen and have larvae that have no legs.
These wasps have a sting that they use to paralyse caterpillars which they gather to feed their larvae.
An interesting feature of wasps and bees is their 'ovipositor', an elongate structure at the tip of the abdomen that is used to lay eggs. In sawflies the ovipositor is saw-like and used to insert the eggs into plant leaves, stems or wood. In parasitic wasps the ovipositor is used to place eggs onto the host or to pierce and insert eggs inside the host. In some species the tubular ovipositor projects well beyond the tip of the abdomen. In other wasps the ovipositor is no longed used to lay eggs. Instead it has become like a hypodermic needle and is used to inject venom, either to subdue prey, or for defence. These are the wasps that can sting. The long tube protruding from the tip of the abdomen in an ovipositor, which is used to insert eggs into the body of a moth caterpillar. Bees usually have a number of special modifications of their bodies in order to gather and carry pollen. Most bees are covered with branching hairs in which pollen grains become entangled. Bees groom this pollen from their bodies with their legs and carry it back to the nest in several ways depending on the species. Honeybees have modified hind legs with a concave area for carrying a ball of pollen. Leaf-cutter bees pack the pollen into a thick mat of hair underneath the abdomen and other bees carry the pollen back inside their guts.
A predatory potter wasp, Delta arcuata.
A Raspberry Sawfly, Philomastix macleayi. Adult sawflies do not have a narrow waist near the base of the abdomen.
A female ichneumon wasp, Leptobatopsis indica.
A Blue-banded bee, Amegilla sp. These bees are solitary, meaning each female constructs her own nest, a burrow in the soil. However, they are often communal, with many females digging burrows in the same area.
Most wasps and bees are active in the daytime. Many visit flowers for nectar or, as in bees, for pollen. Predatory and parasitic wasps are seen on the ground, among vegetation or on tree trunks searching for hosts or prey. Mud-dauber and potter wasps visit the edges of pools and dams to gather mud for their nests.
Wasps and bees undergo abrupt metamorphosis with larvae as the immature stages. The larvae of sawflies, the most primitive wasps, are almost all vegetarians, feeding on leaves or boring into wood. The larvae of most other wasps are carnivores, usually feeding on other insects.
The caterpillar-like larvae of sawflies are mostly vegetarians like these
ones feeding on paperbark leaves.
In parasitic wasps females use their ovipositor (egg-layer) to deposit eggs on or inside a host. Usually the host is the larvae of another insect. The parasitic larva slowly consumes the host, often from the inside, eventually killing it.
Parasitic wasps, like this Lissipimpla excelsa, have a tubular ovipositor
at the tip on the abdomen which is used to lay eggs on or into a host.
The larvae of this species are parasites of moth caterpillars that live in
Predatory wasps are a little different, gathering prey to feed their larvae and bringing it back to a nest. In predators, the ovipositor is not used to lay eggs but is a sting used to paralyse the prey. The prey depends on the species of wasp but it is usually other insects.
The nest may be a burrow in the ground, an abandoned beetle burrow in wood or something that the female wasp builds from mud or plant resin. The nest can have several cells, usually one for each wasp larva. The female puts one or several prey in each cell, lays an egg inside and closes it up. The wasp larva hatches from the egg to find a food supply waiting.
A female Bembix octosetosa, a predatory
wasp that uses the spiny front legs to make a
burrow in sandy soil. It captures and paralyses
adult flies as a food source for her young.
Bees are similar to predatory wasps. They also make nests and gather food for their larvae. The main difference is that, instead of insects, they gather pollen and nectar.
The larvae of bees are also vegetarians, feeding on pollen and nectar.
The solitary carpenter bee, Xylocopa aruana, is one of Australia's
The vast majority of predatory wasps and bees are solitary. The means that each female makes a nest on her own and catches prey to feed her own young. These wasps and bees can use their sting for defence, but only if they really need to, and usually they aren’t aggressive. Some wasps and bees are social, meaning they live in colonies where one or a few females (queens) lay the eggs and the others hunt and rear the young. These wasps and bees will use their stings to defend the nest. They can afford to be aggressive because if a few die the colony will still continue. Paper wasps are a classic example of aggressive social insects that have a sting and are not afraid to use it.
Paper wasps, like Ropalidia impetuosa, are social insects that live in
colonies that they vigorously defend with painful stings.