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Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere
CJAI 21, July, 2012
doi: 10.3752/cjai.2012.21
Nathan M. Schiff, Henri Goulet, David R. Smith, Caroline Boudreault, A. Dan Wilson, and Brian E. Scheffler

Urocerus flavicornis (Fabricius), n. stat.

Fig. C24.1, Schiff et al. 2006: 72, 73 (female habitus)
Fig. C24.2, Schiff et al. 2006: 71 (male habitus)
Fig. C24.3 (map)

Sirex flauicornis [recte: flavicornis] Fabricius, 1781: 418. Type female (HMUG), not examined. The spelling  flavicornis, introduced by Gmelin (1790), is in prevailing use. Type locality: “Labrador Americae”.
Sirex bizonatus Stephens, 1829: 342 (nomen nudum).
Sirex bizonatus Stephens, 1835: 114, pl. 36, fig. 2. Holotype female (BMNH), not examined. Synonymy by Cresson 1865b: 247; accepted by Smith 1979: 128, Harrington 1882a. Type locality: “near London”.
Urocerus riparius MacGillivray, 1893: 244. Lectotype male (INHS, Webb 1980), designated by Frison (1927), not examined. Synonymy by Bradley 1913: 18; accepted by Smith 1979: 128. Type locality: Skokomish River, Washington. Described from “2 males.”
Urocerus flavicornis; Bradley 1913: 18 (change in combination); Fitch 1858a: 45, under U. abdominalis; Burks 1958: 16.
Sirex latifasciatus Konow, 1898: 77 (not Westwood, 1874: 114, pl. XXI, fig. 2).
Urocerus gigas flavicornis; Benson, 1943: 39 (change in rank); accepted by Middlekauff 1960, Smith 1979: 128.

Diagnostic Combination

Among females with light reddish brown protarsomeres 2–5 [gigas and sah], those of U. flavicornis are recognized by the black pronotum and tergum 9. Males are recognized by a black head and pronotum, black abdominal segments 7–9, and, in North American specimens, by the narrow metatarsomere 1 (5.5–8.0 times as long as high).



Color. Head black except for white spot behind eye, spot extending from ventral edge of eye almost to postocellar furrow (Fig. B4.12). Maxillary palp and mandible black. Scape, pedicel, and flagellum light reddish brown, and apex of last flagellomere not darkened. Thorax black (Fig. B4.8). Coxae, basal 0.5–0.7 of pro- (Fig. B4.4) and mesofemur, and metafemur (except extreme apex) (Fig. B4.10) black; tibiae and tarsi light reddish brown (in most specimens, metatibia with brown cloud in apical 0.3 on inner surface) (Fig. B4.10). Fore and hind wings basically clear. Abdomen black, but light reddish brown on terga 1 (some specimens), 2, 7, 8 (basal half of almost all specimens) and 10 (cornus only) (Fig. B4.1).

Head. Vertex densely pitted between the white genal spots. Surface below genal white spot widely pitted.

Thorax. Metatarsomere 2 in lateral view about 2.0 times as long as high, and its tarsal pad about 0.8 as long as ventral length of tarsomere.

Abdomen. Median basin of tergum 9 with base (outlined by two lateral black longitudinal furrows) about 1.6 times as wide as median length, with maximum width about 1.7 times as wide as median length, and with median length about 0.4 times as long as cornus length. Cornus in dorsal view constricted near base, and minimum width of constriction about 0.8 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; tergum 9 with dorsal surface lateral to median basin smooth and without meshes, and ventral surface with meshes and flat sculpticells. Sheath. Length 0.7–0.9 times length of fore wing, apical section 1.1–1.5 times as long as basal section. Ovipositor. Lancet with 24–32 annuli (annuli in basal 0.5 of lancet outlined but difficult to see); junction of basal and apical sections of sheaths aligned between 5th and 6th, or 6th and 7th annuli; apical part of lancet with 14–20 pits. Pits 0.2–0.3 as long as an annulus, becoming gradually small, and disappearing at base of apical sheath section. Edge of last 7–9 annuli before teeth annuli extending as ridge to ventral margin of lancet.


Color. Head capsule black, except for white spot behind eye extending from ventral edge of eye almost to postocellar furrow. Flagellum black or brown to light reddish brown in basal half. Thorax black. Legs black but pro- and mesotarsus, and pro- and mesotibia (brown dorsally in a few specimens) reddish brown; basal 0.25 of metatibia and basal 0.25 and extreme apex of metatarsomeres 1 light reddish brown (Figs. B4.64 & B4.62 hind leg). Fore and hind wings clear. Abdomen black, but light reddish brown on most of terga 3–6.

Head. Vertex densely pitted between the white genal spots. Surface below genal white spot widely pitted.

Thorax. Metatibia 6.8-9.0 times as long as maximum width (Fig. 4.64). Metatarsomere 1 in lateral view 5.5–8.0 times as long as maximum height (Fig. B4.62).

Taxonomic Notes

The types of S. flavicornis, S. bizonatus and U. riparius were not examined, but the descriptions match our concept of U. flavicornis.

Urocerus flavicornis has long been regarded as a subspecies of U. gigas. We have seen specimens of U. gigas from Kamchatka and from Alaska. They show no evidence of gene flow. Moreover, the information from morphology and DNA barcoding shows a clear difference between the two populations. Therefore, we consider them as specifically distinct.

Females are easily distinguished from other species of Urocerus in the Western Hemisphere but males have been commonly mixed in collections with those of U. albicornis despite a paper by Peck (1937) distinguishing them by the proportion of the length and height of metatarsomere 2. Males of U. flavicornis are quite similar to those of U. gigas, but are distinguished on color pattern and, for most specimens, by the proportions of metatarsomere 1 and metatibia.

Biological Notes

Males of U. flavicornis have been observed aggregating at the highest spot of a mountain top where they wait to intercept females (Chapman 1954).

Hosts and Phenology

The host range of U. flavicornis is wide (Felt 1906 [under U. abdominalis], Essig 1926, Burks 1958: 16, Middlekauff 1960, Cameron 1965, Morris 1967, Kirk 1975, Smith, 1979: 128). Based on 51 reared and confirmed specimens, all but one host are Pinaceae: Abies concolor (13), A. lasiocarpa (4), Larix occidentalis (2), Picea engelmannii (3), P. glauca (19), P. sitchensis, P. sp. (1), Pinus banksiana (3), P. contorta (1), P. strobus (4), and Pseudotsuga menziesii. One specimen has been reared from Thuja occidentalis (Cupressaceae).

Based on 338 field-collected specimens, the earliest and latest capture dates are June 25 and November 17. The main flight period is from early June to the first half of September with a peak in the second half of July and the first half of August. Twenty-seven males were caught at hill top in Montana from late June till early September (Chapman 1954).


CANADA: AB, BC, MB, ON, PI, NB, NF, NS, NT, NU, QC, SK, YT. MEXICO: Uncertain record mention by Cameron (1883) without a specific locality. USA: AK, CA (Middlekauff 1960), CO, ID, ME, MT, NH, NY, OR, PA, UT, WA, WY. Urocerus flavicornis is known from all forested regions of Canada and the United States (Harrington 1882a, Rohwer 1928, Weber 1950, Burks 1958: 16, Cameron 1965, Smith 1979) (Fig. C24.3). It was recorded as an interception in Réunion Island (Bordage 1914) and England (Cameron 1890, Benson 1943).

Specimens studied and included for the distribution map: 914 females 122 males from BYUC, CASS, CNC, DEBU, EDUM, GFLC, LECQ, LEMQ, MNRQ, NCSU, NFRC, OSAC, PFRC, UAM, UASM, UCRC, USBD, USFS–AK, and USNM.

Specimens for molecular studies: 32 specimens. See Fig. E2.4c.

CANADA. Ontario: 2007, SIRCA 039, 620; 2007, SIRCA 040, 619. USA. Alaska: 2005, CBHR 231, 658. Colorado: 2005, CBHR 560, 658; 2005, CBHR 561, 658; 2005, CBHR 562, 658; 2005, CBHR 563, 658; 2005, CBHR 564, 658; 2005, CBHR 565, 658; 2005, CBHR 566, 658; 2005, CBHR 567, 658; 2005, CBHR 568, 658; 2005, CBHR 569, 658. Montana: 2006, CBHR 324, 658; 2006, CBHR 325, 658; 2006, CBHR 326, 658; 2006, CBHR 330, 658; 2006, CBHR 332, 658; 2006, CBHR 333, 658; 2006, CBHR 335, 658; 2006, CBHR 336, 658; 2006, CBHR 337, 658; 2006, CBHR 338, 658. Oregon: 1999, CBHR 12, 658; 1999, CBHR 105, 658; 1999, CBHR 106, 658; 1999, CBHR 107, 658. Utah: 2008, CBHR 1950, 658. Washington: 2005, CBHR 208, 625; 2005, CBHR 224, 658; 2005, CBHR 234, 658; 2005, CBHR 250, 658.