Horntail or wood wasp is the common name for any of the 100 non-social species of the family Siricidae, of the order Hymenoptera

Hymenoptera

Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...

, a type of xylophagous sawfly. This family was until recently believed to be the sole living representative of the superfamily Siricoidea

Siricoidea

The superfamily Siricoidea is an archaic group of the order Hymenoptera, consisting of three families of xylophagous sawflies. The group is well-represented in early Tertiary and Mesozoic times, but a number of living taxa remain, including the family Anaxyelidae, which has recently been linked to...

, a group well-represented in early Tertiary

Tertiary

The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 and Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 times, but the family Anaxyelidae has recently been linked to this group.