Why are wasps so irritating in late summer?

Instead of being able to enjoy the last days of summer sunshine, we are often driven inside by the persistent buzz of wasps attempting to get at our food and drink. Wasps have been around all year, so why is it that they only become so irritating at the end of summer?

The answer actually lies in the unusual ecology and bizarre anatomy of social wasps.

In the spring, queen wasps wake from hibernation and start to build their nest, laying eggs and raising their first brood of daughters. These worker wasps cannot produce fertilised eggs, so spend their time helping their mother to expand the nest and raise more young.

One of their main jobs is searching for soft-bodied invertebrates to feed the developing larvae. Bizarrely, adult wasps cannot digest the food they catch because their gut is so constricted by their thin ‘wasp waists’. Instead the workers chew up the prey and feed it to the larvae. In return, the larvae produce a sugar-rich spit that the workers can drink.

The colony will go on expanding throughout the summer until the queen decides to produce males and new queens. After these ‘reproductives’ have left the nest, the old queen stops laying. This means the workers no longer have access to larvae. Instead, they live on the sugar produced by rotting fruit. This can be a problem because fermenting fruit contains alcohol, so wasps can become intoxicated and rather irritating.

They are also attracted to the abundance of sweet foods that humans provide. To a starving wasp, a jam sandwich or a can of coke is just too tempting to avoid. For this reason, wasps are generally only a nuisance in late summer. Remember that these drunken workers don’t have long to live, and as soon as the winter weather sets in the entire colony will die, leaving only the new queens to hibernate through to next year.

Posted in: Minibeasts on 13 July 2015

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