Fig. C20.1 (live female)
Among genera with antennal sockets quite close (inner edges of antennal sockets 1.5-2.0 times as long as distance between inner edge of eye and outer edges of socket) [Sirex, Sirotremex, Xeris, and Xoanon], both sexes of Urocerus are recognized by the mesoscutum with dense pits on the lateral third, pronotum with anterior vertical surface densely pitted, the gena mainly smooth with a white spot dorsally, and the lack of a ridge behind the eye.
Color. Black portions of body without metallic reflections.
Head. Antennal sockets with distance between their inner edges 1.5–2.0 times distance between inner edge of eye and outer edge of socket (as in Fig. B1.4). Distance between inner edges of lateral ocelli about as long as distance between outer edge of lateral ocellus and nearest edge of eye (Fig. B4.13). Maximum distance between outer edges of eyes less than maximum width of head (thus, in frontal view, genal edges completely visible and not intersected by outer edges of eyes). Minimum distance between inner edges of eye about 1.3–1.6 times as long as maximum eye height (as in Fig. B1.2). Gena without ridge behind eye and almost always with white spot in dorsal half (Figs. B1.42 & B1.69), with large pits, each with posterior edge not raised as a low tooth. Head with setae sharp at apex. Antenna with 13 or more flagellomeres (the smallest specimens have the lowest number), and middle flagellomeres in dorsal view 2.0–3.5 times as long as wide; in female, middle and apical flagellomeres with sensory pits over all except on outer surface, and apical 5-10 flagellomeres with sensory oval impression on dorsal and ventral surfaces; and in male, with sensory pits on inner surface to almost all or all surfaces, and apical flagellomeres without sensory oval impressions.
Thorax. Pronotum densely pitted over most of anterior vertical surface (Fig. B1.73). Mesoscutum entirely and densely pitted (including lateral third). Mesotarsomere 1 in lateral view not enlarged, its dorsal and ventral edges almost parallel and base of tarsomere at most 0.7 times its maximum width. Metatibia with two apical spurs, in male, metatibia in lateral view 5.5–9.0 times as long as maximum width. In female, metatarsomere 2 in lateral view 1.5–3.0 times as long as maximum height. Metatarsomere 5 as long as metatarsomere 2 or shorter than metatarsomeres 2 + 3. Fore wing with apex acutely and angularly rounded, with vein 2r–m joined to cell 2M (Fig. B1.71), with vein 2r–m present, with cell 1Rs2 clearly wider than long, with cell 3R1 3.5–4.5 times as wide as long, with cell 2R1 about 0.5 times as wide as cell 3R1, with vein 2r-rs joining stigma near middle; stigma gradually attenuated even distal to junction with vein 2r-rs (as in Fig. B1.25), with vein Cu1 absent, very rarely a short stub, with vein 1cu–a joining vein Cu about mid way between veins 1m–cu and M, with vein 2A extending along wing posterior edge for about 0.4 times cell length (Fig. B1.71), and with vein 3A absent (Fig. B1.71). Hind wing with anal cell 1A (Fig. B1.44); hamuli clearly present both basal and apical to junction of veins R1 and C (as in Fig. B1.11).
Abdomen. Female. Cornus in dorsal view long, narrow, and lateral edges usually constricted at base or (in a few Asiatic species) not constricted (Fig. B1.75). Tergum 9 with median basin with lateral edges markedly divergent and straight then rounded near lateral angle and sharply outlined for about 0.5 times median length of basin, and with basin base (outlined by black furrows laterally) 1.1–1.5 times as wide as median length (Fig. B1.75). Cercus present but very small and wart-like. Sheath. Length of basal section 0.6–0.8 times as long as apical section; apical section without longitudinal lateral ridge, and with teeth (absent in a few species of Urocerus from China) in apical third of dorsal margin and each tooth with bristle near apex (as in Fig. C1.19). Ovipositor. Lancet with any of annuli 3–9 aligned with junction of basal and apical sections of sheath; first tooth annulus without pit; annuli anterior to first annulus before teeth annuli with small pit, and edge of last and preceding annuli above pit and before teeth annuli obtusely produced or sometimes straight (Fig. C20.2).
Urocerus is very diverse, with 33 species restricted to the Northern Hemisphere. Taeger and Blank (2011) and Taeger et al. 2010 recorded 32, but we raised U. flavicornis to species level. There are 28 known Palaearctic species mostly in Asia (Taeger and Blank 2011, Taeger et al. 2010) but only 7 New World species. One introduced species is recorded from Chile; the remaining species (one introduced and five native) are recorded from Mexico north to the tree line in North America. Because we studied only 11 Palaearctic species in addition to the Nearctic ones our generic concept may be incomplete and one should expect that some Asiatic species may not fit one or more character states described above.
The 7 species treated are: