Wasp season looms again

Waimarino Bulletin, Volume 2, Issue 25, 20 November 1984, Page 5

Wasp season looms again

With the onset of summer and the warmer weather Waimarino residents can expect a return of the annual plague of wasps ... they are already appearing in increasing numbers. The Waimarino Bulletin is providing this two-part study of wasps prepared by the Ministry of Agriculture and Fisheries and the DSIR in the hope that a better understanding of their life cycles and habitats will lead to more effective control and destruction of this nasty, even dangerous, pest and predator. We suggest you cut out and keep this first instalment to accompany next week's follow-up.

The German wasp (Vespula germanica) was accidehtally introduced to New Zealand in 1944, and since then it has spread rapidly throughout the country. It is a serious nuisance in some places, and can cause financial loss in orchards, vineyards, and berryfruit gardens. The German wasp has a serious economic impact on beekeeping because it robs honey from hives, sometimes leading to the death of the colony. In the late 1970's another wasp was accidentally introduced into New Zealand. It is known as the common wasp, Vespula vulgaris, and looks very similar to the German wasp V. germanica. Both species have a conspicuous pattern of black and yellow stripes on the abdomen. They are slightly larger than a honey bee and have a smooth, rather than hairy, body. The three features that distinguish the two wasp species are: a black face marking, the colour of the nest, and black markings on the abdomen. Both species have a black marking on the face: in V. vulgaris this has a conspicuous anchor shape; while in V. germanica the marking is reduced and may only consist of a few dots. V. germanica build their combs and nests of grey wasp paper, but in V. vulgaris nests the paper is light- or reddish-brown in colour. The two species have different markings on the back of the abdomen, but these are quite variable in each species and are not a completely reliable guide. Generally, V. germanica has black spots separate from the black stripes, while in V. vulgaris these spots are usually joined to the stripes. So far ( 1 983) V. vulgaris is only found in central Dunedin, Wellington, and the Hutt Valley. This species will probably spread quite rapidly throughout New Zealand, and will cause problems for both beekeepers

and the general public. Its life history is similar to that of V. germanica and the same control measures are effective. Life History of the German Wasp Mated queen wasps hibernate in many sheltered

positions, often in stacks of wood, piles of sacks, or beneath loose bark. In spring these queens emerge from hibernation and fly about looking for nesting sites in banks, hollow trees, or other suitable places. A queen wasp will construct a small nest, only 30 or 40mm in diameter, in a cavity and start laying eggs almost immediately. Until the first generation of young wasps emerge the queen is involved in building the nest, gathering food, and feeding the larvae. These

jobs are taken over by the first worker wasps to emerge, and from this point on the queen restricts her activities to egg-laying. During late spring and early summer the population of the nest increases. The workers continue to excavate the cavity if it is in the ground, and extend the nest with wasp paper (chewed wood fibres mixed with saliva). In late summer and early autumn, drone or male wasps are produced in the nest. As the population of the colony has usually reached a high level by this time, foraging workers begin to collect more sweet (carbohydrate) foods. This supplements, but does not replace, the protein which up until now constituted their diet. The dietary processes of a wasp colony are in fact very complex, with a great deal rff mutual feeding (trophallaxis) being carried out. Worker wasps feed larvae with proteins (and some carbohydrates) and the larvae produce a type of saliva which is relatively rich in carbohydrates and breaxdown products of proteins. This saliva is fed back to the adult wasps, including the queen. New queen wasps are produced late in the autumn, and after mating and returning to the nest they seek another place in which to spend the winter. Normally the drones and workers continue to forage for food, but ultimately they feed on one another and any remaining brood, until the nest is empty. The life cycle is continued next year by queens emerging from hibernation. Overwintered nests can cause serious damage to bee colonies. In places where severe frosts are uncommon, or where there is a constant supply of food, nests headed by a functional queen or even several queens may continue throughout the winter. In the following spring these colonies can increase to an enormous size, and may possibly remain active for a further season if conditions are suitable. Next week we will publish recommended wasp control and destruction methods.