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Know your wasp before it knows you

For a start, not all wasps sting. This information would have been handy when I was collecting firewood recently. Swarms of Asian paper wasps during the heat of the day restricted me to early morning excursions and others have reported similar frustrations when wanting to harvest fruit or work in the garden.

Upon taking a closer look, the husband – an ecologist – realised that nearly all of the swarms menacing us at our home in Gordonton, Waikato, were male.

And males don’t sting, he assured me. The stinger on wasps (and bees) is a modified ovipositor – the organ used by other insects to lay eggs – and only females have them.

He proved his point later that afternoon when he caught a male paper wasp and gently held it between thumb and finger. The little varmint was trying its best to sting the blazes out of him, but not having the necessary equipment, was endearing instead.

The point is – if you can identify and sex the wasps you’re seeing you can work out if you have to back off or whether you can cheerfully continue.

So where are the females, while the males are out, for the most part dancing alone? This year’s queens and workers are coming to the ends of their lives and are dying off with the cooler weather, but their final act has been to produce a new generation of queens, who are looking for somewhere to spend the winter. Which is why they come into houses to lurk in places where they might sting the unwary. A friend was recently stung by a wasp in a discarded dishcloth; another found one in the washing on her line. Our woodshed fills up with wasps at this time of year, and gloves are required when getting the evening’s firewood.

What wasp is that?

There are several species of introduced wasps in New Zealand, some of which are pests of tree crops, but there are four that are generally considered to be pests by the general public – the German wasp, the common wasp, the Asian paper wasp, and the Australian paper wasp.

German wasp (Vespula germanica)

These have been in the country since the 1940s, and were the wasps of my childhood. They are quite large insects, 12 to 17mm long, and are bright yellow with relatively small amounts of black. They have a row of small black dots down either side of the back and, if you want to look that close, there are three dots in a triangular pattern in the middle of the face (or sometimes two black dots like nostrils, and a vertical black midline). They are aggressive, and will sting humans and animals with little provocation. Their nests are made from paper, quite large (often about the size of a football but can be much bigger), and usually underground. The queens, which appear in the autumn, are obvious from their larger size. Hibernating queens tuck their wings under their legs, so that at first sight they may appear wingless.

Common wasp (Vespula vulgaris)

Common wasps are very like German wasps, but have more extensive areas of black – the bands across the back usually incorporate the black dots so that these don’t stand out as separate. There is a black anchor–shaped marking on the face rather than the three dots. Their sting is also nasty. They became established in New Zealand only in the 1970s, but they are now the main wasp in beech forests. They’re arguably the biggest wasp pest in New Zealand, though there are some areas, such as here in the Waikato, where they’re less common than German wasps.

Asian paper wasp (Polistes chinensis)

These guys are slenderer than the German and common wasps, from 13 to 25mm long, and since their first appearance near Auckland in 1979 they have spread throughout the North Island and the northern part of the South Island. Round here there seem to be more and more every year. They are yellow and black and have long legs which dangle beneath their bodies during flight. For most of the year only females are seen, but in the autumn males appear.

If you have a bunch of paper wasps at your place, have a closer look and see if you can tell how many females you’ve got, since they are really the only ones to worry about. They stand out among the males as being bigger and blacker. They have faces which are striped yellow and black, while males’ faces are almost entirely yellow; males also have antennae that are curled at the end, and more extensive yellow colouring overall, especially on their undersides. If you’re struggling to see the differences, try spraying a few and checking them out more closely once they’re dead. But be careful, because it’s possible to get a sting even from a dead female.

Paper wasps gather fibre from wood and plants, which they mix with saliva to form small paper nests, usually up to about 10cm in diameter. These mostly hang from vegetation or under eaves, but can also be in more confined spaces such as under roofing tiles. Asian paper wasps are considered to be less aggressive than German wasps, but will still actively defend their nests – and themselves.

Australian paper wasp (Polistes humilis)

These sensitive souls don’t like frosts and live in warmer, coastal areas of the northern North Island where they can be very abundant. They’re slightly smaller than Asian paper wasps and orange-brown in colour. I’m not very familiar with this species and haven’t been able to find much information about the males, but they’ll be smaller and have the typical curly antennae.

Dealing to paper wasp nests

Although it is tempting to have a crack at them as soon as you discover the nest, wait until evening or first thing in the morning when the wasps are, literally, chilled.

We – well, the husband – has destroyed at least 20 paper wasp nests this season and we’re still discovering them. He notes where the nest is and then comes back later with the flyspray and gives the whole nest a generous dose. Once the wasps are gone remove the nest and burn it if possible, as other wasps will plunder it for material for their own building projects.

German wasp nests

These are a little trickier to deal with but they can be destroyed. If you can’t find where your wasps are coming from try to follow their flight path to discover their nest. You can (carefully) flick white flour on the critters to make them more conspicuous and easier to track – in the evening when the angle of the sun is low they stand out better.

Visit the local hardware shop and buy yourself some Carbaryl-based insecticide powder, then get yourself some tubing, about a metre long and 10mm in diameter. Dip one end of it a few centimetres into the Carbaryl powder and (taking great care not to inhale it!) puff the powder into the entrance to the nest. First thing in the morning when the wasps are cool and quiet is the best time for this.

Dang – I’m stung. Now what?

Usually wasp stings cause only local reactions but sometimes severe allergic reaction occurs – ring 111 if needed.

  • If stung on the neck, face or in the mouth, take an antihistamine and see a doctor immediately. Stings can cause swelling in the throat, making it difficult to breathe.
  • Otherwise, apply an ice pack on the area, or apply antihistamine cream (and take it easy for the rest of the day.)

Things could be worse – at least we don’t have Japanese giant hornets in this country! 

  • Thanks to David Riddell for help in compiling this article and for wasp wrangling.

Postscript:

Recently at Waikorea Beach, between Raglan and Waikato Heads, we found another species of wasp washed up dead along the high-tide line. After a bit of research we learned it was a female yellow flower wasp (Radumeris tasmaniensis). These Australian wasps were first seen in this country only in October 1999, near Cape Reinga, and have since been found as far south as the Bay of Plenty. They lay their eggs on the larvae of large scarab beetles, which in New Zealand seems to be mainly the sand scarab, found in sand dunes, so their distribution is mostly coastal. Because they may pose a threat to native scarab beetles they are regarded as Unwanted Organisms in New Zealand, but they are otherwise largely harmless, feeding as adults on flowers, and not known to sting people.

Yellow flower wasps are large (up to 3cm long, males are smaller), with black and orange stripes on the back, and none of the black dots that common and German wasps have. The undersides are mostly black with narrow white stripes. They have a characteristic flight pattern, flying in horizontal figure-eights, up to a metre above the ground.

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