See text Horntail or wood wasp are any of the 150 non-social species of the hymenopteran family Siricidae, a type of wood-eating sawfly.

[1] A typical adult horntail is brown, blue, or black with yellow or red parts, and may often reach up to 4 cm (1.6 in) long.

Once the egg hatches, the six-legged, whitish larva uses its jaws to begin excavating a long tunnel in which it will live until it is fully grown.

Upon maturity, the larva will spin a silken cocoon and change into a pupa, but before this, the larva takes the precautionary measure of advancing the 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.

Wood-rotting fungi found in horntail tunnels cause very rapid deterioration of the wood and quickly reduce opportunities for timber salvage.

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