A North American wasp, the western yellowjacket (Vespula penylvanica) is a serious predator of native insects.
Photo: Judy Gallagher | CC BY 2.0
This wasp has a striking black and yellow pattern. Australia has some black and yellow wasps (plus some wasp-like flies) but they lack most of the following features.
- The antennae are black (or mostly black).
- When viewed from above, the black eye does not meet up with the black on the top of the head.
- The first segment of the abdomen has a black diamond pointing towards the rear.
- There are many hairs on the head and body.
- During flight the legs remain bent in the landing position rather than dangling below the body.
- The foraging and nesting habits are distinctive – see under Behaviour and Location.
Identifying features shown here include the black antenna, the yellow ring around the eye, and the hairiness. The eye is not always completely surrounded by yellow. Photo: Sarah McCaffrey | Museums Victoria
Yellowjackets have a head and body about 12 millimetres long. Their forewings are 8.5-10.5 millimetres long. Queens are larger but not often seen.
Behaviour and location
Yellowjackets will visit picnics and barbecues to sample sweet foods and meat, attracting attention by landing on plates of food and drink cans. They also visit bowls or pet food, rubbish bins, animal and insect carcases and nectar-bearing flowers.
Instead of building exposed nests like those of paper wasps, they nest in cavities, usually in holes in the ground but sometimes walls or hollow trees.
These western yellowjackets are feeding from a dead grasshopper. Photo: Zion National Park
The only wasps in Australia that bear a close resemblance are other foreign wasps, including two close relatives (Vespula species) accidentally introduced from Europe to south-eastern Australia. These are an environmental threat and a nuisance to humans, and their nests should be destroyed when found, but there is no prospect of eradicating them, except in Western Australia, which has kept them out of the state by running a European Wasp Surveillance and Eradication Program.
The European wasp (Vespula germanica) has all the above-mentioned features, except that the black on the eye meets the black on the top of the head, rather than having separation by a yellow band. It is common in south-eastern Australia, occurring as far north as the Sydney and Bathurst regions. It sometimes turns up in Western Australia, after travelling across in vehicles, where it is subject to eradication.
European wasp (Vespula germanica). Photo: Fir0002 | GNU Free Documentation License 1.2
The English wasp (Vespula vulgaris) of Europe has all but two of the features listed for the western yellowjacket: it has the black on the eye meeting up with the black on the top of the head, rather than being separated by a yellow band, and it has no diamond on the first abdomen segment. This wasp became established in Tasmania, Victoria and in South Australia around Adelaide, but it has declined since the arrival of the German wasp.
English wasp (Vespula vulgaris). Photo: Don Horne | CC BY 4.0
The European paper wasp (Polistes dominulus), found in temperate Australia, is readily distinguished from yellowjackets by the following: antennae and wings that are mostly orange-brown, a black eye that meets the black head, and legs that dangle when it flies. It is slightly longer (about 16 millimetres long) and thinner than a yellowjacket and the abdomen is more gently curved at the front. In Australia is found from Hobart to Adelaide. The Asian paper wasp (P. chinensis) is another introduced species, found in eastern Australia, that displays these differences.
European paper wasp (Polistes dominulus). Photo: Fritz Geller-Grimm | CC BY-SA 2.5
Western yellowjackets can sting repeatedly. Their jabs produce sudden pain, which is often followed by inflammation and redness and sometimes itching. Medical attention should be sought if there is an allergic reaction.
Take a photo of a wasp when it lands on food. The wasps are not aggressive while feeding but anyone approaching them should take care.
Who to tell
Think you’ve found western yellowjackets?
Who to contact depends on where in Australia you are.
If you find this wasp in Western Australia contact the Pest and Disease Information Service (PaDIS) on 08 93683080 or via email@example.com. They are committed to eradicating European wasps and related species.
If you find them elsewhere in Australia should phone 1800 900 090 and ask for the office of Australia’s Chief Environmental Biosecurity Officer.
If you do not receive a satisfactory response within a week email us via our contact form. Please do not contact us in the first instance.
Since arriving in Hawaii the western yellowjacket is having dramatic impacts because hives are sometimes reaching enormous sizes, containing more than half a million wasps, which is far more than in their native range. They prey on insects and spiders so effectively that in Hawaii Volcanoes and Haleakala national parks, caterpillar and spider densities have fallen by 86% and 36% respectively. Many other insects are hunted. The wasps are aggressive ‘nectar thieves’, reducing seed production by Hawaii’s dominant tree, ohia (Metrosideros polymorpha), by taking its nectar without spreading the pollen, and by displacing the insects that do provide pollination. As well as draining the nectar crop each morning, they prey on bees at a ‘surprisingly high’ frequency. Native Nesodynerus wasps also suffer from yellowjackets, which compete with them for ohia nectar and caterpillar prey.
In its native range in the western USA the western yellowjacket is a serious human nuisance. Every few years population outbreaks associated with warm, dry springs create severe problems for people recreating outdoors and harvesting timber and fruit. People are often stung when they disturb nests in houses, gardens and parks and suffer serious swelling and blisters. The wasps gather at picnics and food dispensing facilities to scavenge sweet foods and meat. They can be serious pests in fruit-growing regions, sometimes halting harvesting operations when workers are stung. The wasps also damage fruit, feeding on grapes and removing the juices, and piercing pears, peaches and other fruits. Several growers in Oregon and Washington have reported losing nearly half their red grape crop. Beekeepers lose hives to attacks from yellowjackets, which harvest the bees until none remain, and in surviving hives honey harvesting is disrupted by wasp stings.
The European and German wasps in Australia are causing many environmental, social and economic problems. For example in Tasmania’s highlands they threaten the endangered Ptunarra brown butterfly (Oreixenica ptunarra).
Yellowjacket queens often overwinter in human goods so they can be transported around the world in shipping containers.
- Invasive Species Compendium: Vespula pensylvanica.
- Natural History of Orange County: Images of western yellowjackets.
- Western Australian Government: European wasp surveillance and eradication program.