tunnel close to the inner bark, so that the mature, winged insect will not have to travel far through the wood and risk damaging its delicate wings, although there is a record of a Sirex-infested tree having been cut into rafters which were used in building a roof and covered with sheet-lead an eighth of an inch thick. One of the rafters contained a Sirex in either the larval or pupal stage; and when the adult insect sought its freedom, it found the way obstructed by the lead. It went right through, apparently finding lead not much more difficult to deal with than bark. Populations increase rapidly only where brood material is abundant. The life cycle usually requires two years, and adults are usually in flight from late July to early September. Wood-rotting fungi found in horntail tunnels cause very rapid deterioration of the wood and quickly reduce opportunities for timber salvage. An ichneumon wasp (Rhyssa persuasoria) lays parasitoid grubs in Sirex, which kill them. Technological inspiration The female wood wasp lays eggs inside trees, and its methods of doing so have inspired scientists to come up with new and safer surgical probes that they expect to be more efficient. The wood wasp ovipositor itself contains two interlocking valves. Each valve is covered with teeth that are backward-facing, with the teeth of one valve catching onto the wood to provide resistance, and the other valve moving forward and taking a slight step. The second valve then catches the wood to provide continued resistance as the first valve moves forward. Thus by quick oscillation, the valves alternate in providing resistance and moving forward, the process itself leads in the ovipositor drilling almost an inch into the sapwood with minimal force being applied and without the ovipositor buckling or breaking. Researchers and scientists inspired by this system have created a prototype neurosurgical probe that works on the same principle. Its needle is made of silicon, with two oscillating valves that are covered with micron-sized teeth that too face backward. This enables it to penetrate deep into the brain causing little damage. According to the New Scientist magazine, "Unlike existing rigid surgical probes, the device will be flexible enough to move along the safest possible route, bypassing high-risk area of the brain during surgery, for example". A probe like this would considerably reduce the number of incisions necessary to access areas that are