Siobla Cameron

Niu, Gengyun & Wei, Meicai, 2010, Revision of the Siobla annulicornis, acutiscutella and sheni groups (Hymenoptera: Tenthredinidae), Zootaxa 2643, pp. 45-65 : 46-47

Siobla Cameron

Siobla Cameron, 1877: 88 –89. Type species: Siobla mooreana Cameron, 1877 , by subsequent designation of Ashmead, 1898.

Encarsioneura Konow, 1890: 240. Type species: Tenthredo sturmii Klug, 1817 , by monotypy. Megasiobla Dovnar-Zapolskij, 1930: 86. Type species: Megasiobla zenaida Dovnar-Zapolskij, 1930, by original designation.

Diagnosis: Head and thorax densely punctured; anterior margin of clypeus subtruncate; mandibles asymmetrical, left mandible bidentate, right mandible simple, without inner tooth or basal lobe; metabasitarsomere compressed laterally; pedicel of antenna longer than wide; inner tooth of claw much longer than outer tooth; anal cell of fore wing with an oblique crossvein slightly beyond middle; lancet slender, distinctly sclerotized, usually without distinct annular suture.

Description: Body robust, head and thorax usually densely punctured; clypeus small, anterior margin subtruncate, sometimes feebly and roundly protruding, or with a small incision; labrum round at apex; mandibles short and stout, asymmetrical, left one with a distinct inner tooth at about middle, right one simple, without inner tooth or basal lobe; malar space about 0.5–1.5x diameter of ocellus in female, or narrower in male; eyes large or medium-sized, inner margins straight, strongly converging downwards; supra-antennal tubercles usually not elevated; middle fovea large, lateral fovea distinct, open anteriorly; frons weakly defined; ocellar triangle small; head behind eyes in dorsal view not elongated, lateral sides converging posteriorly; occipital carina sharp and complete; antenna about as long as or longer than abdomen but clearly shorter than thorax and abdomen together, pedicel longer than wide, third antennomere much longer than fourth antennomere; anterior collar of pronotum narrow with broadest part about two times diameter of ocellus; ventral margins of propleura narrowly and roundly meeting; anterior margin of mesoscutellum truncate, furrow before mesoscutellum very deep, transverse; metanotum with a deep and broad basin before metascutellum, distance between cenchri about two times width of a cenchrus; metapostnotum strongly constricted, linear on meson; epicnemium absent, mesepisternum without ventral thorn but with a sharp anterior marginal carina, mesepimeron broad, with a transverse ridge at middle, metepimeron narrow with a small dorsal lobe, posterior corner not extending posteriorly; first abdominal tergite with distinct middle suture and a small blotch; inner tibial spur of fore leg bifurcate; hind coxa normal, not strongly elongated; apex of hind femur extends beyond apex of abdomen; hind tibia longer than hind femur and second trochanter together, inner tibial spur about as long as or shorter than half length of metabasitarsomere; metabasitarsomere strongly compressed laterally, distinctly shorter than following four tarsomeres together; claw without basal lobe, inner tooth much longer than outer tooth; fore wing with cu-a meeting cell 1M at about basal 1/7, apex of vein R distinctly turned down, vein R+M much shorter than cu-a, first abscissa of vein M parallel with 1mcu, anal cell with an oblique cross vein slightly beyond middle; hind wing with cell Rs and M closed, anal cell shortly petiolate, marginal vein in male absent; lancet slender, distinctly sclerotized, usually without distinct annular sutures; penis valve simple, very narrow or elliptical.

Whilst some species are apparently narrowly oligophagous (e.g. S. sturmii on Impatiens species), others may be polyphagous, as seems to be indicated by records of S. ruficornis on plants of various families in the foodplant list by Verzhutskii (1981). Liston (1995, 1997), Taeger (1998) Lacourt (1999) and Schmitz (2007) mentioned hostplants of Siobla species. Nakamura (1962), Takeuchi (1949) and Lee et al. (2000) recorded some hostplants of S. ferox .

The limited existing data suggest that most Siobla are univoltine. Overwintering is in a leathery cocoon: emergence may sometimes take place after two winters ( Malaise 1931). Larvae of Siobla are unusual in appearance, because they possess large, thorn-shaped, fleshy processes (described by some authors as “spines”) on the dorsum of thorax and abdomen ( Lorenz & Kraus 1957; Ahola 2001). After the last larval moult, these processes are lost.

PLATE 1. Siobla zuoae Wei, 2005 . (a). Veins of fore wing; (b). Veins of hind wing; (c). Cells of fore wing; (d). Cells of hind wing.