Wasps and bees belong to the order Hymenoptera – one of the largest insect groups, which includes ants. Hymenoptera adults nearly all have a narrow waist, between the thorax and abdomen. They have two pairs of membranous wings, the front pair larger. Some are wingless.
Many species form colonies and have a social structure with specialised roles, but others live alone. In some species the female’s ovipositor (egg-laying tube) doubles as a stinger. Males do not sting.
Wasps and bees are similar in most respects – bees are really a sub-group of wasps. Wasps have few or no hairs. Most wasp larvae feed on invertebrates, and adults mainly on sugary food such as nectar.
Bees have hairy bodies. They are totally vegetarian, and mostly feed their larvae on pollen.
The Hymenoptera life cycle has four stages:
New Zealand has an estimated 2,000–3,000 species of wasp and bee, most of which are native. The exact number is not known, as new species are still being found. Most are not very noticeable, and many are tiny. Groups include wood wasps and sawflies, parasitic wasps, stinging wasps, hunting wasps and bees.
More easily seen are the introduced German and common wasps, paper wasps, honeybees and bumblebees. They form a tiny fraction of the total number of species, but they cross our paths more often.
The sawflies and wood wasps are a primitive group, separate from all the other Hymenoptera. Early in the evolution of wasps, this group stayed relatively unchanged, while the ancestors of most of today’s wasps developed a narrow waist and other features.
New Zealand has only three native species of primitive wasp, all hard to find. Little is known of their biology and diet, but most of this group feed only on plant tissue.
The best known is a parasite, Guiglia schauinslandi, which eats the larvae of wood-boring beetles and other wood wasps.
Several accidentally introduced sawflies and wood wasps have become very common. Some, like the pear and cherry slug (actually the larval stage of Caliroa cerasi), and the eucalyptus blotch leaf miner (Phylacteophaga froggatti), are pests of cultivated plants. Larvae of the European sirex wood wasp (Sirex noctilio) feed in the wood of conifers, particularly radiata pine, and can cause considerable damage in plantation forests.
The most common primitive wasp is the willow sawfly (Pontania proxima). Its larvae feed inside willow leaves and make the leaf grow into a hard, reddish lump or gall, seen all over New Zealand.
Parasitic wasps are by far the largest group of wasps. They do not sting, but the females use their needle-like ovipositor (egg-laying tube) to place eggs on or inside another insect, usually its egg, larva or pupa.
When the wasp larva hatches from the egg, it feeds on its host – at first on non-essential body tissues so as not to kill it too quickly. Eventually it consumes the host. The fully fed wasp larva then forms a pupa, and eventually an adult parasitic wasp emerges.
Parasitic wasps use a wide range of hosts. Some attack only eggs, others only larvae, others pupae. Only rarely do they attack adult insects. Some species lay a single egg per host, others several. Some eggs are laid on the outside of the host’s body, others are injected inside it.
Each parasitic species usually attacks just one or a small group of related species. This makes them useful for controlling insect pests – many parasitic wasp species have been brought into New Zealand for this purpose. For example, the parasitic wasp Apanteles glomeratus helps control white butterfly, a pest to horticulture.
The tiny fig wasp lives and feeds inside growing figs. As it enters a fig to lay its eggs, it also fertilises the plant with pollen carried on its body. Each species of fig has its own species of pollinating wasp. New Zealand has two Australian wasp species, which pollinate the Moreton Bay and Port Jackson fig trees.
Most of New Zealand’s native wasps are parasitic, and new species are constantly being discovered. Recently a whole new family (Maamingidae) was found in New Zealand; this family is found nowhere else.
Most are small – the size they can reach is limited by the size of their host. The smallest, with a body length under 1 millimetre, develop inside small hosts like insects’ eggs, or scale insects. The largest, 4 centimetres long, is Certonotus fractinervis, which attacks the fleshy wood-boring larvae of the native elephant weevil (Rhyncodes ursus). The female drills its long ovipositor into dead beech tree trunks to find a larva of the weevil.
Within their natural ecosystems, native parasitic wasps act as natural enemies that control populations of native insects. Many live in leaf litter. Some have reduced or absent wings, so they cannot fly, and look rather like ants. One of these, Betyla fulva, is a natural parasite of the native glow-worm. It attacks glow-worm pupae in the bush and in damp gullies, but apparently not those living in caves.
A single egg of one tiny species of parasitic wasp divides into 1,000–2,000 embryos inside a single green looper caterpillar. Each embryo then becomes a wasp larva. The larvae wait until the caterpillar is fully grown before they eat it out. The caterpillar dies while starting to spin its silken cocoon.
Some associations between parasitic wasps and their hosts are ancient. For example, several species of a primitive parasitic wasp (Archaeoteleia) parasitise the eggs of the cave wētā. The presence of closely related but different Archaeoteleia species in Chile indicates a common ancestry going back at least to the Cretaceous period. At this time, up until 85 million years ago, New Zealand and Chile were joined in the supercontinent of Gondwana. Cave wētā are also found in other lands that were once part of Gondwana, and it seems probable that their eggs have been parasitised by Archaeoteleia for at least the last 85 million years.
Compared to most countries, New Zealand has few native stinging wasp species – just 29, in two families. They can give a painful sting, but only under extreme provocation. All are solitary hunting wasps, not naturally aggressive to humans, being more intent on finding food for their offspring.
The 11 species in the Pompilidae family all prey on spiders, which they paralyse with venom and then drag into their 'nest' – usually a hole in the ground. Here they lay an egg on the paralysed spider, which becomes the only meal the wasp larva ever has, from the time it hatches until it is fully developed.
The golden hunter (Sphictostethus nitidus) hunts on the ground for the large brown vagrant spider (Uliodon species) and the tunnel-web spider, and in bushes for nursery-web spiders.
The large black hunter (Priocnemis monachus) prefers large, ground-dwelling spiders, including tunnel-webs and trapdoor spiders that make lidless burrows in the soil.
The 18 species of the Sphecidae family (the closest relatives to bees) prey on various insects and spiders. The commonly seen mason wasp (Pison spinolae) makes nest cells of mud, and stocks them with paralysed orb-web spiders.
The most offensive stingers are four introduced species of social wasp in the Vespidae family. These are pests in urban, rural and natural ecosystems. The worst two are of European origin, the black-and-yellow German and common wasps (Vespula germanica and Vespula vulgaris respectively), which attack and sting to defend their huge nests. Both species, especially the common wasp, have invaded native forest – kauri forests in the north and beech forests in the south.
These wasps eat vast numbers of native insects, in direct competition with insect-eating birds. They also feed heavily on beech forest honeydew, an important food for native insects and birds such as kākā and bellbirds. Their numbers are highest in late summer, and in some South Island beech forests their combined weight may exceed that of all the birds. They can make outdoor recreation unpleasant and hazardous.
Bee and wasp venoms are a complex mix of proteins, serotonin and histamine. It’s the histamine that causes pain and swelling. Medical help is usually only necessary for stings in the mouth and throat, and for hypersensitive and allergic people (0.5–2% of the population). Some may suffer anaphylactic shock and death. On average, two people die from wasp or bee stings every three years in New Zealand.
These wasps make papery nests from dry plant fibre mixed with their saliva. The two introduced paper wasp species prefer life in the open – in city and suburban gardens, farmland, scrub and open country. They make nests in shrubs and small trees, under the eaves of buildings, or even hanging from fencing wire. Their nests are small – a suspended ‘umbrella’ of paper cells. Towards the end of summer this reaches a maximum diameter of 7.5 centimetres, with about 200 cells.
The Australian paper wasp, Polistes humilis, a black and reddish-brown species with yellow markings and legs, arrived in the late 19th century.
The Asian paper wasp, Polistes chinensis, arrived in New Zealand more recently. It has the black-and-yellow pattern associated with wasps.
Both species are abundant in the northern North Island. The Asian species is still spreading south and may become established throughout New Zealand. Both are voracious predators of small insects, particularly caterpillars of various moths and butterflies. The Asian paper wasp captures monarch and copper butterfly caterpillars, and is blamed for the apparent decline in copper butterfly numbers.
Like wasps, bees may be solitary or social. They feed on nectar and pollen, and play an important role in the pollination and survival of many flowering plants. New Zealand has 28 native and 13 introduced species of bee.
At least three native bee species have a basic social structure, a bit like the introduced honeybee and bumblebee. The rest are solitary, although they may make nests close together.
Native bees pollinate many native plants. They are also widespread in kiwifruit and apple orchards and some vegetable crops, and may be important pollinators in horticulture.
The most commonly seen native bees are 18 species of Leioproctus. These bees are robust and hairy, looking similar to honeybees but smaller (5–12 millimetres long). All are black except for the South Island species Leioproctus fulvescens, which is covered with dense orange–yellow hair. They are often seen in summer carrying pollen on their back legs, like honeybees and bumblebees.
They dig nest holes in the ground, and sometimes a nesting area riddled with bee holes gives the impression of a colony. A small pile of soil is the usual sign of individual nest tunnels. Each species prefers a specific type of soil. For example, Leioproctus fulvescens needs fine-grained soil, while Leioproctus metallicus nests in coastal sand.
The seven Hylaeus species are 7–9 millimetres long, and slender. Almost hairless, they are black with small yellow markings on the face and thorax. They make nests in blind tunnels in twigs and branches, or in old beetle holes in logs. They have no special pollen-carrying structure on the back legs, so carry pollen in the stomach.
The smallest (4–8 millimetres long) and most easily overlooked native bees are four species of Lasioglossum. They are black or greenish, only moderately hairy, and nest in the soil. At least one species, Lasioglossum sordidum, has adapted well to modified habitats. Its nests are often found along fencelines, on horticultural land sprayed bare with herbicides, and on stopbanks and ditch sides above water level.
Honeybees (Apis mellifera) are the familiar golden-orange and brown species, brought to New Zealand from England by settlers for honey production and plant pollination. The first documented introduction was to the Hokianga, Northland, in 1839.
Honeybees visit more flowering plant species, including many native plants, than any other bee. They are of huge economic importance, vital for the pollination of many fruit, vegetable and seed crops, and they produce honey, beeswax, pollen, royal jelly and propolis. New Zealand’s 300,000 commercial hives produced 9,000 tonnes of honey a year on average between 2001 and 2005.
Honeybees have a social structure within the colony or hive. Each colony has one egg-laying queen (15–20 millimetres long), a variable number of drones – all males – and many thousands of sterile female workers (11–15 millimetres long).
Workers build a regular honeycomb structure of hexagonal cells where food – nectar and pollen – is stored and larvae develop. They also gather nectar, pollen and sap, manage honey production, and feed the larvae, queen and drones.
A breakaway group of bees with a queen may swarm and form a new, feral colony. These tend to be in hollow places – tree or rock cavities, and hollow walls or ceilings of buildings.
A beekeeper’s artificial hive mimics a wild hive, but is designed to simplify the management of the bees and their honey.
Accidental introduction of the damaging parasite of the varroa mite (Varroa destructor) to the North Island has affected the honey industry there since 2000, and is responsible for the almost total elimination of feral honeybee colonies there. By 2006 it had spread to the South Island.
Four species of bumblebee (Bombus) were introduced from England in 1885 and 1906 for pollination and seed production of red clover. Their longer tongues can reach inside red clover flowers, which the shorter-tongued honeybees cannot do – although they are excellent pollinators of the smaller white clover flowers. Bumblebees are sometimes used to pollinate greenhouse and orchard crops.
Only females (queens and workers) have a sting, but they are not aggressive and usually sting only if disturbed or handled roughly.
Bumblebees have a social structure, and they build nests in dry cavities – abandoned rodent nests, rabbit burrows, wood piles, compost heaps, old stuffed chairs and sofas, under houses or in walls.
The nest cells are oval or almost spherical, made in irregular horizontal layers rather than the neat combs of the honeybee. Colonies are also smaller – by January to February (summertime), there are about 200 workers in a mature colony of the large earth bumblebee (Bombus terrestris).
Nests run down in late summer and are often destroyed by invading rodents, insects, mites and slaters. The foundress queen dies, but new queens leave the old nest and overwinter in small cavities they excavate in the soil.
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