The oviposition biology of siricid woodwasps in Europe.
In connection with investigations on the infestation of pines in Australasia by Sirex noctilio F., the oviposition behaviour of 8 species of siricids (S. noctilio, S. juvencus L., S. cyaneus F., Urocerus gigas (L.), U. augur (Klug), U. fantoma (F.), U. sah (Mocs.) and Xeris spectrum (L.) is described from investigations in the laboratory and an outdoor insectary in southern England on infested timber that was collected in Europe, North Africa and Turkey. Females of all species except X. spectrum injected arthrospores of the symbiotic fungus Amylostereum into the wood during drilling, from paired mycangia at the base of the ovipositor. Species of Sirex made 1-4 drills for every insertion of the ovipositor through the bark; single drills rarely contained eggs, and drills without eggs contained more fungus than those with eggs. The drills of Urocerus spp. were always single and relatively long and contained several eggs, with fungus deposited in masses between each egg. X. spectrum, which has a thinner and more flexible ovipositor, made 1-5 branched drills with up to 9 eggs per insertion, and was attracted for oviposition to timber that was already infested, or to sawdust that had been inoculated with Amylostereum.The eggs of the siricids are described, and information is given on adult fecundity, life-span and mucus glands and reservoirs. It is suggested that the reason why S. noctilio has become a pest in Australia is related to the copious secretion of a phytotoxic mucus, which, in combination with the symbiotic fungus, is lethal to living trees.