Wood Wasp (Sirex)

A moderately large wasp that is black or metallic blue, often with yellow bandings. The long lancelike ovipositor (egg-laying organ) of the female wood wasp is used for drilling holes into wood. Usually a single egg is deposited into each hole and the larva on hatching bores through the heart wood causing much damage.

The common wood wasp Sirex juvencus is about 30 mm/1.1 in long and blue-black with a metallic sheen. The male may be distinguished from the female by its short triangular spine or horn at the tip of its abdomen and also by a brown-red stripe on its back. The female lays her eggs in conifers.

The giant wood wasp Urocerus gigas is found in Britain. The female, which measures up to 40 mm/1.6 in long, has a drill-like ovipositor with which she bores holes into the wood of conifers where she deposits her eggs. She may also sometimes attack other wood, such as poplar or ash. In general, she drills holes into old or unhealthy trees. The larvae tunnel into the wood and may take up to three years to mature.