The adult is approximately 20 – 40 mm long. They are usually brown or black marked with yellow. Both male and females have a tail, but only the females have an ovipositor – usually longer than the tail. It is not a wasp at all as it has no “wasp waist” that all bees, wasps and ants have. Wood wasps are usually found in forests that have sunny clearings. They are fast and noisy fliers, and fly only when it is sunny, usually from May onwards. Female adult length is 24 – 44 mm, male adult length is 12 – 32 mm. The antennae are many-segmented.
Also although the female – and it is usually just the female wood wasps we see – looks fearsome, she is quite harmless. The very worst she can do is fly into you. This is a typical example of a harmless insect gaining protection from predators by mimicking a harmful one. The long, dark brown thing sticking out of her rear end is not a sting, but her ovipositor. With it she drills vertically 5 – 10 mm into wood – usually a diseased, unhealthy or dead conifer – and injects 4 – 8 eggs.
Males are rarely seen as they tend to fly around the tops of trees only when the sun shines looking for a mate. The eggs hatch in around 4 weeks and the larva spends its time eating the wood-destroying fungi that its mother thoughtfully injected along with the egg. At the base of the ovipositor there is a pair of glands that contain the fruiting bodies of the fungus, and some of these are injected with each egg.
The larval stage lasts for 2 1/2 – 3 years, and the tunnel they make can be 30 cm long. The final larva length can be as much as 40 mm. Before pupation they tunnel to around 1 cm from the tree surface, then pupate, so that when the adult emerges it has only 1 cm of wood to gnaw through to reach the outside.
If you suspect you have a wood wasp infestation in Edinburgh, Glasgow, Aberdeen, Dundee or Perth, call GRAHAM pest control today and we could help.