It looks sunny at the moment: corona measures have been relaxed, the economy has not completely collapsed, the vaccination rate is steadily rising and the activities that are allowed again can be carried out in summer heat. Nevertheless, vigilance is advised. Right now.
If it literally looks sunny outside, you can sometimes see small, shiny insects landing on stilts, bee hotels, walls and sandy paths and walking around nervously, their antennae constantly moving. At first glance, they may look a bit like brightly colored flies. But they are wasps: golden wasps.
Most of the golden wasps (Chrysidinae) found in the Netherlands can be found near the nests of other solitary wasps and bees. These so-called hosts fill brood cells in their nests with provisions for their larvae. For bees, this consists of pollen and nectar, and for wasps from other arthropods such as flies, beetles, caterpillars and spiders. High protein foods. Just as protein is the bee or wasp egg that is laid with the provisions, and the larva that crawls from it to eat it.
This valuable stock is what a golden wasp with her nervous running and flying is looking for. Once she has found a nest of the host, she penetrates there to lay an egg of her own. Once that egg hatches, the larva will make a meal of the host’s egg or larva, after which it will feast on the provisions in the brood cell. Gold wasps are therefore parasites. Their larvae grow up at the expense of the brood of other species. They are also known as cuckoo wasps because, like the bird, they lay eggs in someone else’s nest and use the care of that other person to raise their own offspring.
As mentioned, vigilance is advised, especially if it looks sunny. While the hard-working solitary bees and wasps fly in and out to provide their future offspring with sufficient food, an uninvited guest can crawl into their nest and make life literally impossible for that brood. And if the golden wasp is caught during her sneaky action, the dreaded sting with which the hosts are armed is virtually useless. They can’t get through the intruder’s armored outer skeleton.
And there is another difficulty. The abdomen segments of these golden wasps have a concave or flat shape that allows them to curl up completely, bringing legs and antennae safely inboard. They become a ball of shine that a stinger or firm set of jaws cannot get a hold of.
With their dazzling beauty, cuckoo wasps make up for their unpleasant natures a bit. They are flying gems in all kinds of shades of red, green and blue, which display a beautiful metallic brilliance thanks to their armored outer skeleton. Gold wasps are a feast for the eyes. But just like in the human world, it is possible that appearances can be deceiving. So vigilance is always advised. It’s not all gold that glitters.
A version of this article also appeared in NRC in the morning of July 9, 2021