Trachionus Haliday, 1833

Cui, Qian, van Achterberg, Cornelis, Tan, Jiang-Li & Chen, Xue-Xin, 2015, The genus Trachionus Haliday, 1833 (Hymenoptera, Braconidae, Alysiinae) new for China, with description of four new species, ZooKeys 512, pp. 19-37 : 20-21

Taxon classification Animalia Hymenoptera Braconidae

Trachionus Haliday, 1833 Figs 1, 2-10, 11, 12-21, 22, 23-32, 33, 34-42, 43-46

Trachionus Haliday, 1833: 265; Dalla Torre 1898: 198 (as synonym of Chelonus Panzer, 1806; Chelonus mandibularis attributed to Haliday, and this undescribed species was synonymized (p. 204) with Chelonus maculator (Dahlbom, 1833)); Shenefelt 1973: 839 (id.); Marsh 1979 a: 231 (id.); van Achterberg 1997: 81 (as valid genus). Type species (by original designation): " Chelonus mandibularis " (= Sigalphus mandibularis Nees, 1816).

Aenone Haliday, 1833: 267 (nom. nud.; not Aenone Lamarck, 1818), 1838: 214; Shenefelt 1974: 1109; van Achterberg 1997: 81 (synonymy with Trachionus Haliday).

Aenone Curtis, 1837: 123 (not Aenone Lamarck, 1818); van Achterberg 1997: 81 (synonymy with Trachionus Haliday). Type species (by present designation): Sigalphus mandibularis Nees, 1816.

Oenone Haliday, 1839: 3 (not Oenone Lamarck, 1818); Shenefelt 1974: 1109; van Achterberg 1997: 81 (synonymy with Trachionus Haliday). Type species (designated by Haliday 1840): Sigalphus mandibularis Nees, 1816.

Symphya Foerster, 1863: 273; Shenefelt 1974: 1109-1111; Marsh 1979: 217; van Achterberg 1997: 81 (synonymy with Trachionus Haliday). Type species (by original designation): Sigalphus mandibularis Nees, 1816.

Anarmus Ruthe (in Brischke), 1882: 138; Shenefelt 1974: 1109; van Achterberg 1997: 81 (synonymy with Trachionus Haliday). Type species (by van Achterberg 1997): Sigalphus mandibularis Nees, 1816.

Planiricus Perepechayenko, 2000: 30 (as subgenus of Trachionus ). Type species (by original designation): Sigalphus hians Nees, 1816.

Diagnosis.

Vein r-m of forewing absent; mandible exodont, with 3-5 teeth or small lobes and second tooth of mandible acute (Figs 7, 17, 28, 30, 39); forewing vein 1-SR longer than 3 × width of vein and distinctly longer than parastigma (Figs 1-2, 11-12, 22-23, 33-34); clypeus transverse (Figs 7, 17, 28, 39) and epistomal suture narrow (subgenus Planiricus Perepechayenko) or as wide as convex part of clypeus and deep (subgenus Trachionus Haliday); ocelli normal (subgenus Planiricus Perepechayenko) or strongly protruding (subgenus Trachionus Haliday); pronope absent; metanotum distinctly and acutely protruding dorsally (Figs 4, 14, 25, 36); anterior half of sternaulus (below the precoxal sulcus) present or absent, only in subgenus Trachionus Haliday posterior half of sternaulus wide and coarsely crenulate; combined length of second and third metasomal tergites of female 0.6 –0.8× total length of metasoma, these tergites at least partly sculptured (Figs 5-6, 15-16, 26-27, 37, 42); fourth and fifth metasomal tergites smooth and of female more or less retracted (Figs 16, 27, 42).

Biology.

Ovo-larval koinobiont parasitoids of Phytobia spp. ( Agromyzidae ) boring in or near the cambium layer in branches of shrubs and trees ( Greene 1914; Clausen 1954; van Achterberg et al. 2012).

Notes.

Up to 1997 the interpretation of the genus Trachionus had been problematical, not the least because of the synonymy with the genus Chelonus by Dalla Torre (1898). It is contradicted by the clear original diagnosis by Haliday (1833): "Areolae cubitales 2; mandibulae hiantes 4-dentes". If the diagnosis of the genus is combined with the diagnosis of the group ("Abdominis segmenta coalita postica retracta. Chelonus") then it is clear that it can only apply to the tribe Dacnusini (because of the exodont mandibles) and to the genus Aenone Curtis, 1837 (because of the Chelonine-like metasoma), a junior homonym and, therefore, unavailable. In 1997 van Achterberg clarified the position of the genus Trachionus and synonymized Trachionus with Symphya Foerster, the oldest available name for the group in current use that time. All four species from China belong to the subgenus Planiricus Perepechayenko (= Trachionus hians -group) because they have the epistomal suture much narrower than the clypeus and the sternaulus is absent or is only anteriorly shallowly developed as punctate area.

Trachionus is similar to two Palaearctic genera, Epimicta Foerster, 1863, and Parasymphya Tobias, 1998, because of the presence of the pronotal spine, and the sculpture and shape of the second and third metasomal tergites. These taxa can be separated as follows:

Key to Chinese species of Trachionus Haliday