Dear Readers, when I was in Somerset last week I was astonished at the number of wasps feeding on ivy flowers outside my Aunt Hilary’s home. The Sputnik-shaped blooms were fairly abuzz with the insects, and it wasn’t until I mentioned it to my Aunt that I realised that I must have been standing a few feet from a nest which the wasps had made in her shed wall. It just goes to show that, provided you don’t interfere too closely with them, wasps are not as aggressive as is sometimes thought.
I have always been fascinated by wasps. In the spring, when I sat at the end of the garden, I would sometimes hear the tiniest of scraping noises. Eventually, I tracked it back to a queen wasp, gnawing at the wooden sleepers that surround the area in order to find material for her nest. I counted twenty separate trips made by a single queen in a fifteen minute period on one warm April morning. The queen starts by building a stalk, called a petiole, which serves as an entrance passageway. She smears this with a chemical that repels ants (who would otherwise eat it). She builds a single hexagonal cell, surrounded by six others, and continues to add to the structure. When she’s built 20-30 cells, she lays an egg in each one, and goes a-hunting for food to nurture the larvae when they’ve hatched. Meantime, the larva, who are hanging vertically in the bottomless cells, have to wedge themselves against the walls to avoid falling out, probably not the best way to spend your developing years.Once the first wasp larvae hatch into workers, the queen settles down to lay more eggs, and will soon lose her power of flight. The workers forage for food for the larvae and the queen, and for wood to make paper to expand the nest. There is not the detailed breakdown of duties that there are in some other social insects, but it has been noted that it’s the younger, faster workers who do the foraging, while the older insects stay at home and guard the nest. In the context of wasps, a worker is ‘old’ at two weeks. The queen, too, will be dead by the end of the year – queens do not overwinter in this country, so it’s the new queens who are out and about in the autumn.
Wasps feed themselves on sweet stuff, such as nectar, but the larvae need protein, and so wasps are extraordinarily adept hunters. I once watched one circling the stem of a cabbage plant. When she spotted a tiny green caterpillar she grabbed it behind the head and tried to prise it from a leaf, while the poor larva held on with its suckered feet. A tug-of-war ensued that went on for several seconds, the wasp buzzing furiously as it flew back and forth, until, finally, the caterpillar was prised loose and carried away, held below the wasp’s body like a bomb below a B52.I also remember eating a salmon sandwich in the cafe outside Kenwood House on Hampstead Heath. A wasp came to investigate and, after a few moments, determined that a morsel of salmon was ‘food’. She cut a long slice from the top edge, and flew away with it, returning a few moments later. As I watched, she systematically cut up the fish. Another wasp popped in for a visit but couldn’t work out what to do with the salmon, and flew off. Then ‘my’ wasp returned for another helping.
I was fascinated by this small insight into wasp behaviour. Firstly, what mechanism was the wasp using to identify something as alien as a chunk of salmon as food? Secondly, why was she able to cut it up so efficiently when her sister couldn’t? Does this imply that wasps, like bees, can learn? It would not surprise me in the least. There have been lots of recent investigations into the intelligence of the more good-natured bumblebee, but to my knowledge no one has been studying these aspects of wasps.
As spring turns into summer, the nest continues to grow in size – a mature nest may contain as many as 8000 individuals. However, once it reaches its maximum, the workers, probably triggered by failing pheromones from the queen, start to build cells that will hold new queens. These are located at the entrance to the nest and, as the workers feed the first larva that they encounter first, it could be that a queen wasp is made simply by the volume of food that she is fed.Certainly there is evidence that when several queens arise in a single nest, it’s the biggest, most well-fed one that usually triumphs. A plump queen is more likely to survive the winter hibernation period than her skinnier rivals, so she has an obvious advantage in passing on her genes.
When I was watching the wasps last week, I noticed one particularly splendid wasp licking an ivy leaf. From her size, I could tell that she was a new queen, freshly emerged from the nest, and from her behaviour I surmised that she was licking up the honeydew left by aphids on the ivy leaf (though she could also have been drinking dew). By early November the original queen is probably dead, so there are no larvae to feed, and no need to go hunting for protein. Instead, it’s every worker for herself, and so the ivy flowers are valuable fuel. None of these ‘ordinary’ wasps will last the winter, however – they will all be dead after the first frost. The nest breaks up, and will normally not be re-used (though the new queen might build a nest close to the original site, or even within the old nest). This is probably to avoid a proliferation of parasites.
Looking closely at the new queen, I was struck by the complexity of her jagged mouthparts, the elegance of those smoked-glass wings, and also that she was rather hairy, something that isn’t obvious when a wasp is just flying past. The pattern on her face tells me that she is a common wasp (Vespula vulgaris) rather than a German wasp (Vespula germanica) – the latter wasps have three little dots above their mouthparts rather than the ‘T’ shape that we see here. Both of these wasps are very common in the UK. If you happen to find an old nest, note that German wasps tend to construct using sound wood, which makes their nests a uniform grey. Common wasps, like the queen on the ivy, use rotten or fallen wood, which makes their nests more variable in colour.
In North America, the yellow-jacket, which was long thought to be the same species as the European common wasp (Vespula vulgaris), was discovered to be a different species (Vespula alascensis), mainly on the basis of dissection of their genitalia. It seems to be one of those cases of a widespread animal developing into a new species once it’s become isolated. For anyone who would like to read further details of the decision and the minutiae of vespid sexual organs, I am linking to the paper here.
For most of the year, we don’t really notice wasps much – it’s not until their numbers increase and they go on the hunt for sugar that they start to ‘make a nuisance’ of themselves. But I have a deep hatred of the wasp ‘lures’ that you see in public gardens, including the cafe at Kenwood. These are filled with sugar water, encouraging the wasps to enter. Once in, they can’t get out and simply drown, creating a hideous wasp ‘soup’ that appals me. It seems like a poor reward for the way that they keep down the numbers of ‘pest’ species that would otherwise be munching through our food plants. I have found that putting a small saucer of beer at the other end of the table often keeps the wasps occupied while the humans are drinking, and that modelling sensible behaviour to young children is a great way to keep them calm and unmolested. And yes, I know that some people are genuinely terrified of wasps, and that some people can go into anaphylactic shock from a sting: you have my utmost sympathy. I just think that, generally, we should avoid killing other living things if there’s a more compassionate, creative solution. It doesn’t seem a lot to ask.
Photo One (Wasps’ nest) – By Donald Hobern from Copenhagen, Denmark (Vespula vulgaris) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Photo Two (Wasp and Horsefly) – By Robert Goossens (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Photo Three (Portrait of Common Wasp) – By Tim Evison, Denmark (User:tpe) (Own work) [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons
All other photographs copyright Vivienne Palmer. Free to use and share non-commercially but please attribute and link back to the blog, thank you!