The unfairly maligned wasps

I saw a wasp upon a wall

And did not like his face at all:

And so the creature had no time

To wonder whether he liked mine.

‘Plain Murder’, A.G. Prys-Jones.

 

The common wasp (Vespula vulgaris) and its close relative, the German wasp (Vespula germanica), are not likely candidates for the most loved insects, but many people are not aware of their ecological value, writes Athayde Tonhasca.

Wasps feed mostly on high-energy sugars and carbohydrates from foods such as nectar and fruit. Because they are not covered with fuzzy hairs, wasps are much less efficient pollinators than bees. Even so, they are thought to be the main pollinators of ivy, which flowers late in the year when the number of bees diminishes and wasps require more nectar to produce males and queens. Because of their high energy content, ivy fruits are important for many farmland and garden birds, so wasps contribute to their food supply.

Wasps for Jim _m204018

Vespula sp. © Caroline Anderson

Adult wasps feed on sugars, but their larvae need protein. Adults provide it by hunting soft-bodied invertebrates such as caterpillars, flies, spiders and beetle larvae.

Researchers in New Zealand estimated that wasps capture ~0.8 to 4.8 million prey items per hectare per season (1.4 to 8.1 kg of prey/ha), which is equivalent to what is taken by all insectivorous birds in the same area. The figures for Britain are likely to be lower, but nonetheless it is evident that wasps are voracious predators, and thus gardeners’ allies.

Picture1

A common wasp captures a horsefly.   © Robert Goossens, Wikipedia Creative Commons

Wasps may spoil your picnic, but without them, your hamper could have been deprived of bread, beer and wine. Yeast – especially Saccharomyces cerevisiae – has been fundamental to baking, brewing and winemaking throughout human history. In nature, yeast cells are found primarily on ripe fruits during the summer months. Since yeast is not airborne, it must rely on vectors to move from plant to plant. For years it has been assumed that birds or bees were responsible for transporting yeast cells, but nobody could explain how they survived the winter. Italian researchers suspected that wasps were involved, because they feed on yeast-harbouring grapes, and their nests are hibernation havens for microorganisms.

The research team analysed samples from vineyards around Italy to find several species and hundreds of strains of yeast in the wasps’ guts. Some were related to wine strains of S. cerevisiae, others were similar to bread strains. Also, yeast survived the winter in the insects’ guts, and was transferred to the larvae via the food regurgitated by the queen. Other organisms such as birds may be involved in the life cycle of yeasts, but wasps seem to be especially important.

Common Wasp nest

Common wasp nest © Richerman, Wikipedia Creative Commons

Wasps are also master engineers. They build their nest with a strong, lightweight and waterproof paper-like material produced by a mix of saliva and scrap wood, which is chewed to a pulp. The queen kick starts it by building a column and coating it with a chemical that repels ants. Then she builds cells around it, all in clusters of hexagonal units. Workers expand the nest by building more cells, ventilating them by vibrating their wings. The cells’ hexagonal configuration maximises strength and efficiency, as this design demands the least amount of energy and building material.

So next time someone asks you what’s the point of wasps, you can say they are fundamental for nature and for us, and they are fascinating creatures with complex social organisation and efficiency. They may be a nuisance now and then, but possible clashes with us are easily avoided.

Wasps are not aggressive outside the nest; when they hover persistently over your bottle of lemonade or sandwich, they are only interested in the food and will not deliberately attack you. The best strategy to avoid a close encounter is by minimizing the chances of attracting them. Do not leave food exposed; keep it in sealed containers and put away any rubbish into lidded bins. If a wasp flies towards your food, wait for it to fly away; flailing your arms increases the chances of entrapping the wasp, which could then sting you.

However, wasps will defend their nest aggressively if disturbed or threatened. If you find yourself near a nest, retreat without producing much vibration or noise. Take care with lawnmowers and other motorized equipment because they may trigger a defensive reaction.