Plagues of wasps

Press, Volume CXI, Issue 32661, 17 July 1971, Page 12

Plagues of wasps

(By SUSAN McLEAN)

Anyone who has spent recent holidays in Northland, the Bay of Plenty or in the Nelson area, will agree wholeheartedly, if not happily, with the official report that there are plagues of wasps in these districts. They appear to be mainly German wasps, one of the more common species, which form communities consisting of perhaps thousands of insects at the end of the summer, and when one knows a little of the wasp’s life story it is perhaps more obvious why the insects are so prevalent in these regions. In the spring, a solitary queen wasp, after mating the previous autumn and hibernating during the winter, seeks out a suitable place for a nest, perhaps, inside a decaying tree or underground in an old mouse-hole, but essentially somewhere warm and dry. When a suitable cavity has been found it usually has to be enlarged, any waste material being pushed outside, and the wasp then sets about lining it with a paperlike substance formed when the wasp masticates tiny wood shavings with its saliva.

A kind of umbrella is constructed within the nest, and the comb, consisting of just a few cells at first, is built beneath this, the open end of each cell being directed downwards. One egg is deposited in each and after a few weeks they hatch into grubs which somehow hang on to the inside of the cell. These grubs have to be fed, and here the wasp is a great asset, as the diet consists of pests such as flies and caterpillars as well as butterflies and moths. Wings, legs and head are severed after the prey has been paralysed and portions of the trunk are masticated and fed mouth-to-mouth to the grubs. After going through a chrysalis stage the grubs

emerge as worker wasps and after a short rest start enlarging the nest and building more cones. The process continues, the queen gradually doing less and less work until all she does is provide the eggs. The cones are built suspended from one another and a nest may have anything from six to 10 at the end of the summer, each consisting of of hexagonal cells containing eggs destined to become worker wasps. However, in the late summer the queen lays some larger eggs which develop into perfect males or females and once these have reached maturity the worker wasps’ toil is over and the diet changes to one of fruit. This phenomenon seems to be sheer indulgence of appetite for there are no grubs to be fed and it is as if they know their last days are coming for wasps dislike the cold and apart from the females which hibernate, all die off in the winter.

Obviously, the three areas mentioned are particularly suited to a wasp’s way of life; the dense native bush affords suitable warm and dry nesting places and also attracts a plentiful supply of caterpillars, moths and spiders; all three regions have a similar climatelong, warm and humid summers and mild winters and although the rainfall is fairly high, underground nests would be protected by the thick forest growth. Little can be done to eradicate the wasps even if that was advisable, although only the queens need be destroyed as they start the colonies. Nature may reduce the numbers in her own time by providing an early cold spell; meanwhile we must take solace in the thought of the number of flies and other pests that must be devoured, after all, the wasps only annoy us for one or two months of the year, even if it is holiday time.