Among females with a completely or almost completely black abdomen, including the cornus [californicus], those of U. albicornis are recognized by the wide white central portion of the flagellum with black or brown flagellomeres at the base and apex. Among males with black abdominal segments 7–9 and with head mainly black [flavicornis and gigas], almost all those of U. albicornis are recognized by the gena partly reddish brown near the mandible, and the anterolateral angle of the pronotum, and metatarsomere 1 relatively short (4.0–5.2 times as long as high).
Color. Head black except for white spot behind eye. Maxillary palp and mandible black. Scape and pedicel black; flagellomere 1 usually 2 in part, rarely 3 and 4 in part black or mainly so, apical flagellomeres 3–8 brown to black, and central flagellomeres white or yellowish (Fig. B4.30). Thorax black. Legs black but white on basal 0.25–0.6 of tibiae and tarsomeres 1 (Fig. B4.5). Fore and hind wings darkly tinted (Fig. B4.32). Abdomen black, or many specimens black with a white spot laterally on tergum 8 (Fig. B4.19).
Head. Vertex densely pitted between the white genal spots (as in Fig. B4.47).
Thorax. Metatarsomere 2 in lateral view about 2.5 times as long as high (Fig. B4.34), and its tarsal pad about 0.8 times as long as ventral length of tarsomere.
Abdomen. Median basin of tergum 9 with base (outlined by two lateral black longitudinal furrows) 1.7 times as wide as median length, with maximum width of basin 1.6–1.8 times as wide as median length, and with median length 0.35 times cornus length. Cornus in dorsal view constricted near base, and minimum width of constriction 0.7 times maximum width subapically. Tergum 8 with microsculpture of sublateral surface (between spiracle and pitted sculpticells on central area) with clearly impressed meshes, and sculpticells flat and hardly elevated posteriorly (Fig. B4.36); tergum 9 with dorsal surface lateral to median basin smooth and without meshes, and ventral surface with meshes and sculpticells flat and hardly elevated posteriorly. Sheath. Length 0.7–0.9 times length of fore wing, apical section 1.18–1.67 times as long as basal section. Ovipositor. Lancet with 24–30 annuli (annuli in basal half of lancet outlined but difficult to see); junction of basal and apical section of sheath aligned between 5th and 6th or 6th and 7th annuli; apical part of lancet with 8–14 pits. Pits 0.12–0.15 times as long as an annulus, becoming gradually very small, and disappearing in basal 0.5 of apical section of sheath. Edge of last 6–9 annuli before teeth annuli extending as ridge to ventral margin of lancet.
Color. Head capsule in ventral third reddish brown or paler at least above mandible to as much as above mandible and clypeus combined, rarely completely black (Fig. B4.50). Scape and pedicel black; flagellum usually pale in basal half, gradually shifting to brown in apical half (Fig. B4.52), occasionally all brown (Fig. B4.53), and rarely completely yellowish. Pronotum light reddish brown at least near anterolateral angle to as much as most of dorsal surface, rarely completely black. Meso- and metathorax black. Coxae, femora, part of pro- and mesotibia in many specimens, apical 0.25–0.3 of metatibia, and most of metatarsomeres 1–3 black; pro- and mesotibia, pro- and mesotarsus, and metatarsomeres 4 and 5 light reddish brown to reddish brown (Fig. B4.63, hind leg). Fore and hind wings clear and slightly dark tinted in apical half of fore wing. Abdomen with terga 3–6 reddish brown, terga 1, 2, 7 and 8 black, side of terga 3–6 often black, and sterna 2–9 mainly black or brown (Fig. B4.66).
Head. Vertex densely pitted between the white genal spots.
The types of S. albicornis and S. magus were not examined, but the descriptions (especially those of the antenna and abdomen) match our concept of this species.
Adults of U. albicornis are evidently strong fliers; specimens have been caught in the alpine zone of Mount Washington, NH (Slosson 1895). Damage by larvae was described by Thomas (1881) and Champlain (1922). Females prefer to attack recently killed or weakened trees (Blackman and Stage 1918).
The host range of U. albicornis is very wide (T. W. Harris 1841, Thomas 1881, Felt 1906, Blackman and Stage 1918, Essig 1926, Bedard 1938, Reeks and Smith 1945, Belyea 1952, Stillwell 1960, Middlekauff 1960, Morris 1967, Smith, 1979: 128). Based on 131 reared and confirmed specimens, all but one host records are Pinaceae: Abies amabilis (1), A. balsamea (14), A. grandis (1), A. fraseri, A. lasiocarpa (1) (Morris 1967), A. nobilis (Benson 1945), Larix laricina (18), L. occidentalis (11), Picea sp. (1), Picea engelmannii, P. glauca (33), P. mariana (11), P. sitchensis, Pinus banksiana (2), P. contorta (2), P. resinosa (3), P. strobus (12), Pseudotsuga menziesii (6) (Morris 1967), Tsuga heterophylla (14), and Tsuga canadensis (Felt 1906). One specimen was recorded from Thuja plicata (Cupressaceae).
Based on 356 field-collected specimens, the earliest and latest capture dates are June 7 and October 4. The main flight period is from the second half of June to the first half of September with a peak from early July to late August.
CANADA: AB, BC, MB, NB, NF, NS, ON, PI, QC, SK. USA: CA (Middlekauff 1960), DC, GA(?), ID, IL, IN, LA, MA, ME, MI, MO, MT, NC, NJ, NY, OR, PA, RI, VA, VT, WA, WV. Urocerus albicornis, a widespread species in forested regions, occurs from southern boreal regions of Canada south to California, New Mexico, Missouri, and North Carolina (Lintner 1898, Blackman and Stage 1918, Rohwer 1928, Smith 1979) (Fig. C21.4). It has been reported as an interception in the United Kingdom (Lintner 1898, Cameron 1890, Benson 1945).
Specimens studied and included for the distribution map: 763 females and 242 males from BYUC, CASS, CFIA, CNC, CUCC, CUIC, DEBU, EDUM, FRLC, GFLC, LECQ, LEMQ, MNRQ, NFRC, NFRN, OSAC, PFRC, USFS–GA, and USNM.
Specimens for molecular studies: 39 specimens. See Fig. E2.4a.
CANADA. British Columbia: 2006, CBHR 451, 658; 2006, CBHR 452, 658; 2006, CBHR 454, 658; 2006, CBHR 455, 658; 2006, CBHR 456, 658; 2006, CBHR 457, 658; 2006, CBHR 458, 658; 2006, CBHR 459, 658; 2006, CBHR 461, 658; 2006, CBHR 463, 658; 2006, CBHR 464, 658; 2006, CBHR 465, 658; 2006, CBHR 467, 658; 2006, CBHR 468, 658; 2006, CBHR 469, 658; 2006, CBHR 470, 658; 2006, CBHR 471, 658; 2006, CBHR 472, 658; 2009, SIRCA 087, 595. Nova Scotia: 2006, CBHR 295, 658; 2006, CBHR 298, 658. Ontario: 2009, CNCS 1072, 608; 2009, CNCS 1073, 591; 2009, SIRCA 029, 616; 2009, SIRCA 030, 614; 2009, SIRCA 031, 615; 2009, SIRCA 032, 619; 2009, SIRCA 033, 615. USA. Minnesota: 2008, CBHR 1372, 658; 2008, CBHR 1463, 658; 2008, CBHR 1472, 658; 2008, CBHR 1473, 658. Montana: 2006, CBHR 327, 658; 2006, CBHR 328, 658; 2006, CBHR 329, 658. New York: 2005, CBHR 199, 658; 2005, CBHR 202, 658. Washington: 2005, CBHR 240, 658; 2005, CBHR 251, 658.