Friday, 26 September 2008

Why Wasps? Not Such A Pest Says Clive S.M. Cohen

Wasps have a bad press. People inherently dislike wasps which are notorious and looked upon as the public enemy of the invertebrate species.
When a queen wasp emerges from hibernation, with the first rays of sun emerging in the early spring, queens seek the nectar of early flowering willow and a suitable nesting site in accordance with their species of which there are now 9, including hornets and 2 new species, Vespa Media and Saxonica. Then, unlike bees, they produce half a dozen hexagonal cells that (instead of being made out of wax), are made out of wood. They protect these cells by a layer of cone shaped fragile balsa wood covering, having produced this from chewing local fence or rotten tree. They then mix it with water in their saliva and produce the substance, as compared with bees from their wax glands.

Soon young wasps emerge and the nest is enlarged by the young wasps taking over from the queen who quickly becomes an egg-laying machine. As the number of cells enlarge, the protective covering is removed internally and replaced outside, in layers, causing the nest to develop in size. Eventually by the end of the season it becomes at least the size of a large watermelon, or larger.

During all this time, the wasps are feeding on aphid, caterpillars, maggots of various species and a vast variety of spiders and other invertebrate species, for which they are endlessly hunting. Without wasps our flora and many species of trees would undoubtedly be stripped of their leaves. Examples of this have occurred recently in West Hendon, where the Brown Tailed Moth has festooned many trees and denuded them of leaves, causing expensive canopy mist-spraying by Council staff.

The feeding habits of most species continue until August/September when their appetite changes with the advent of less invertebrates on which they so readily feast and the availability of apple, plum and pear on which their appetite then becomes focused. It is at this time of year that most people are aware of the presence of wasps that become drunk on the alcoholic content of the rotting fruit and can sting on impact. Colonies die in their entirety in October/November, and this year will be as late as December because of the wet weather. This is after the production of young queens and their mating, who then hibernate until the following spring.

There are however some species which are the exception in their habit and diet. The tree wasp for example can consume exclusively caterpillars and complete their life cycle as early as July/August, when most of the caterpillars have finished for the season.

Hornets which are massive and intimidating, in common with bumble bees, are not aggressive unless their nesting site is threatened. In recent years hornets have spread from East Barnet and are largely present throughout the Borough of Barnet. Currently, they can be seen hawking for honey bees at the entrance of beehives, or even a wasp colony and recently a further new species is spreading throughout the United Kingdom from Southampton, where it was first observed, and is called "the bee woolf". This species lines its nest specifically with honey bees!

There are also over 200 species of solitary wasps that feed entirely on other invertebrates, as well as a large yellow and black windhover which, while feeding on pollen, lays its eggs in the debris at the bottom of a wasp’s nest.
Wasps undoubtedly, much maligned as they are, contribute to the quality of our environment. Unfortunately because of their presence frequently close to human habitat, it is necessary for colonies to be destroyed in accordance with health and safety risks. But there is every reason to suppose that this should be done as selectively as possible, so that we do not succeed in destroying an entire species.

(From The Greenacre Times September 2008)

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