Insects of Britain and Ireland: the families of Hymenoptera

DELTA home

L. Watson and M. J. Dallwitz


Horntails, Wood-wasps.

Adults large; 15–40 mm long; not conspicuously spherical-headed and ‘necked’ (i.e., unlike Xiphydra).

Head. Sub-antennal grooves present. Antennal segments 14–30.

Thorax. Pronotum deeply indented or emarginate at the back. Mesoscutellum completely separated from the scutum laterally by defined axillae. Cenchri present. Fore-wings with a conspicuous pterostigma; with the venation well developed. Hind-wings with closed cells. Hind tibiae without specialised spurs.

Abdomen. The abdomen broadly sessile at its base, without a marked constriction. The gaster concolorous, or colour-patterned; when concolorous, black, green or blue; when patterned, blue-, green- or black, and yellow or orange. Ovipositor of females visibly protruding (slight but obvious, and the last abdominal segment characteristically with a conspicuous, horn-like projection); adapted for boring.

Larvae. Larvae legless or the legs vestigial (and no abdominal prolegs); phytophagous (tunelling in wood).

General comments. Fore tibia with only one apical spur, or with two differing greatly in size; and the pronotum viewed from above shaped like a bow tie, by contrast with its cap-shaped appearance in Xipydriidae.

British representation. Species in Britain 11 (probably only two indigenous, plus five established introductions, and the rest so far associated only with imported timber); Sirex, Tremex, Urocerus and Xeris.

Classification. Suborder Symphyta; Superfamily Siricoidea.

Illustrations. • Sirex juvencus (Fir-destroying Wood-wasp: B. Ent 253). • Sirex juvencus (details, B. Ent. 253). • Sirex juvencus (dissection details, B. Ent. 253). • Sirex juvencus: B. Ent. 253, legend+text. • Sirex juvencus: B. Ent. 253, text cont.. • Sirex juvencus (Cameron II, vii). • Uroceras gigas (Great Wood-wasp: Cameron II, vii). male. female. • Uroceras gigas (dissection details: Cameron II, vii). 6a, ovipositor: 1,triangular plate, 2 oblong plate, 3, sheath of latter, 4, borer (homologous with sawfly saw). 6b, triangular plate and top of oblong plate from beneath. 6c, apex of borer. 6d, apex of last abdominal segment (hypopygium). 6e, hypopygium from above: 1, anus. 6f, trophi (mouthparts): 1, maxilla, 2, labium.

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the families of Hymenoptera. Version: 16th May 2016.’.