Horntail, common name for insects related to the sawflies. Horntails, also called wood wasps, differ from sawflies chiefly in having a strong, drilling ovipositor (egg-laying organ) rather than a sawing ovipositor. The common name is derived from the shape of a spearlike plate at the end of the abdomen. Females deposit eggs in the bark of trees, and the larvae are wood borers, living within the tree for as long as two years before they pupate and emerge, leaving a hole about 6 mm (about 0.24 in) in diameter in the timber. They are rarely common enough to do significant damage. The adults are much larger than sawflies; a common species, the pigeon horntail, averages 6 cm (about 2 in) in length and has a wingspan of about 6 cm.
Scientific classification: Horntails make up the family Siricidae, in the order Hymenoptera. The pigeon horntail is classified as Tremex columba.