A READER has contacted me about a wasp’s nest built into a curtain that had been left open all summer.
The nest was abandoned, as it would be at this time of year, but he was amazed by its intricate construction. It appeared to be made of paper and there were holes in his papers in the room, and he wanted to know if the wasps had made the holes.
There are different wasp species in Ireland. They are in two categories — solitary and sociable. Solitary wasps don’t build nests and sociable wasps do. The curtain builder was a social wasp and probably Vespula vulgaris, the common wasp. They have an interesting life-cycle. It starts on a warm day in early spring when a queen wasp emerges from hibernation. She flies around looking for a nest site and starts to build. The nest is made from wood, which is chewed and mixed with saliva to produce a paper- or card-like substance — other materials, such as plastic or paper, are occasionally used.
The queen had mated with a male wasp the previous autumn and stored his sperm in her body. She now lays fertilised eggs in the chambers in the nest. This continues until the nest is the size of a walnut and the first eggs hatch. These turn into sterile female worker wasps, who take over the building of the nest, while the queen lays eggs — up to 25,000 in a season. The nest can end up as small as a tennis ball or as large as a football, or larger in a very successful colony.
The female workers hunt for food for the larvae, paralysing insects and spiders with their sting, chewing them up, and bringing them back to the nest as high-protein pellets. In return, the larvae produce a sweet, sticky substance, which the workers lick off for nourishment. In late summer, the last of the larvae hatch into fertile male and female wasps, which leave the nest and mate. Because there are no larvae left in the nest, there’s no more sweet, sticky stuff, so wasps become annoying at the end of summer — they’re looking for a substitute food. If one stings you, or if you kill one, a pheromone is released that attracts other wasps and makes them prone to sting. It’s wiser to leave them alone.
In the autumn, all the wasps die except for the young, newly mated females, who go into hibernation to emerge as queens the following year. When they do, they seldom, if ever, re-use a nest. They build a new one. Most people thoroughly dislike wasps, and the internet is full of ways to kill them and destroy their nests. But they play an important role ecologically.
Birches are easy trees to recognise, particularly at this time of year when the leaves have fallen, revealing the characteristic black and silver bark. Young trees have copper-coloured bark. There are two native Irish species, along with a number of cultivated varieties. They are silver birch (Betula pendula) and downy birch (Betula pubescens). They can be hard to tell apart, though downy birch, which is commoner in the wild, tends to have more black and less silver in the bark and the ends of the twigs don’t tend to droop, as they do in silver birch. The two species can hybridise, in which case it may take a geneticist to find out what’s what. They are widespread on acid soils and are one of the few species that will actually grow in pure peat. However they will not tolerate being shaded by taller trees and are uncommon in mixed woodland. The timber can be used for plywood and furniture and makes good firewood. The twigs are used to make hurdles for horse racing.
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