Insects of Britain and Ireland: the families of Hymenoptera

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L. Watson and M. J. Dallwitz


Stem Sawflies.

Adults small to large; 4–10 mm long (mostly), or 11–18 mm long (Hartigia).

Head. Antennal segments 16–30.

Thorax. Pronotum more or less straight at the back. Cenchri absent. Fore-wings with the venation well developed. Hind tibiae without specialised spurs.

Abdomen. The abdomen broadly sessile at its base, without a marked constriction (with a slight constriction only). The gaster concolorous, or colour-patterned; when concolorous, black or dark coloured; when patterned, black-and-yellow or brown-and-yellow. Ovipositor of females not visibly protruding.

Larvae. Larvae legless or the legs vestigial (the legs vestigial, and prolegs lacking); phytophagous (boring in stems, with Hartigia and Janus on dicot trees and Rosaceae, the rest on Gramineae and sometimes damaging cereal crops).

General comments. Slender insects, the body more or less cylindrical or bilaterally compressed.

British representation. Species in Britain 12; Calameuta, Cephus, Hartigia, Janus, Trachelus.

Classification. Suborder Symphyta; Superfamily Cephoidea.

Illustrations. • Calamenta, Cephus, Janus, Trachelus (Cameron III). • Janus femoratus (Curtis), Yellow-thighed Cephus: B. Ent. 301. • Janus femoratus (detail): B. Ent. 301. • Janus femoratus (dissections): B. Ent. 301. • Janus femoratus (B. Ent. 301, legend+text. • Janus femoratus: B. Ent. 301, text cont.. • Janus femoratus (Cameron II, vii). female. 1a, mandibles; 1b, labium; 1c, maxillary palpus. • Calamenta filiformis (Cameron II, vii). female. 3a, maxillary palpus. 3b, ovipositor: a, cerci; b, oblong plate; c, attachment of the latter; d, saw; e, triangular plate; f, hypopygium. • Hartigia linearis (Cameron II, vii). male. 2a, mandibles; 2b, maxillary palpus; 2c, 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.’.