header image
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 cressoni Norton

Fig. C23.1, Schiff et al. 2006: 68, 69 (female habitus)
Fig. C23.2, Schiff et al. 2006: 67 (male habitus)
Fig. C22.6 (map)

Urocerus Cressoni Norton, 1864: 16. Holotype female (ANSP), examined by DRS. Cresson 1928: 10, Ries 1951: 84, Marshall 2000 (male photograph). Type locality: “Pennsylvania”.
Urocerus tricolor Provancher, 1868: 17. Holotype female (ULQC), examined by DRS (Smith 1975a). Synonymy by Ries 1951: 84; accepted by Smith 1975a: 302, Smith 1979: 128. Type locality: Trois Rivières, QC (Norton, 1869: 362).
Sirex dimidiatus Westwood, 1874: 115, pl. XXI, fig. 5. Holotype female (OXUM), images prepared by James E. Hogan and sent to HG for study. Synonym by Cresson 1880: 67; accepted by Smith 1979: 128. Type locality: “America Septentrionalis”.
Sirex tricolor; Kirby, 1882: 382 (change in combination).
Sirex Fiskei Ashmead, 1904: 63. Holotype female (USNM), examined by DRS. Synonymy by Konow, 1905b: 321; accepted by Ries 1951: 84, Smith 1979: 128. Type locality: Tryon, North Carolina.
Sirex cressoni var. tricolor; Bradley 1913: 21 (change in rank).
Urocerus cressoni var. unicolor Bradley, 1913: 22, fig. 31. Holotype female (ANSP), examined by DRS (Smith, 1975). This name is treated here as infrasubspecific as mentioned clearly by Bradley. Based on the International Code of Zoological nomenclature (1985), article 45(c) stipulates that an infrasubspecific name is excluded from the species group and the provisions of the code do not apply to it. Synonym by Ries 1951: 84; accepted by Smith 1979: 128. Type locality: Joliette, Quebec.

Diagnostic Combination

Among both sexes with the basal 0.3–0.7 of the flagellum black and sharply separated from the white apical section [taxodii], females are recognized by the reddish brown terga 6–10, and males by the black thorax and legs.



Color. Head black except for white spot behind eye (Fig. B1.64). Maxillary palp and mandible black. Scape and pedicel black, flagellum (Fig. B4.16) black in basal 0.3–0.6 (usually flagellomeres 2–10), and white in apical 0.4–0.7 (apex of last flagellomere almost always darkened, rarely completely white or dark brown). Thorax black. Coxae and femora (except apex of profemur in a few specimens) black. Tibiae and tarsi highly variable in extent of white pattern. Extreme dark pattern: pro- and mesotibia, pro- and mesotarsus, apical 0.8 of metatibia and apical 0.9 of metatarsomere 1 black; extreme pale pattern: apical half of protibia and mesotarsomeres 3, 4 and apical half of 5, apical 0.2 of mesotibia and apical half of mesotarsomeres 3–5, none of metatibia and none of metatarsus black; common pattern: metatibia and metatarsomere 1 black in apical 0.6–0.9, remaining tarsomeres black (Fig. B4.27), mesotibia and mesotarsomere 1 with black more extended on hind leg, protibia and protarsomere 1 mostly black except at base. Fore and hind wings very darkly tinted with purple reflections. Abdomen reddish brown, or terga 1 up to 1–6 black (tergum 2 usually whitish yellow) (Fig. B4.3).

Head. Vertex densely pitted between the white genal spots (Fig. B4.47).

Thorax. Metatarsomere 2 about 2.0 times as long as high (Fig. B4.27), and its tarsal pad about 0.5 as long as ventral length of tarsomere (Fig. C23.3).

Abdomen. Median basin of tergum 9 with base (outlined by two lateral black longitudinal furrows) 2.0 times as wide as median length of basin, basin 2.2–2.5 times as wide as median length, and median length of basin 0.25–0.30 times as long cornus length (Fig. B1.75). Cornus in dorsal view constricted near base, and minimum width of constriction 0.7–0.8 times maximum width of cornus subapically. Tergum 8 with microsculpture of sublateral surface (between spiracle and pitted sculpticells on central area) with clearly impressed meshes, and sculpticells raised and scale-like (thus, surface matt) (Fig. A3.14); tergum 9 with dorsal surface lateral to median basin smooth and without meshes (Fig. B4.25), and ventral surface with meshes, and sculpticells scale-like and slightly elevated posteriorly. Sheath. Length 0.85–0.95 times length of fore wing, apical section 1.18–1.54 times as long as basal section. Ovipositor. Lancet with 26–32 annuli (annuli in basal 0.5 of lancet outlined but difficult to see); junction of basal and apical sections of sheath aligned between 5th and 6th, 6th and 7th, or 7th and 8th annuli; apical part of lancet with 17–22 pits. Pits 0.25–0.3 times as long as annulus, becoming gradually small, and disappearing at the base of apical sheath section or on subapex of basal section; edge of last 8–10 annuli before teeth annuli extending as ridge to ventral margin of lancet.


Color. Head capsule (except white genal spot, and in many specimens reddish brown surface of capsule below eye often including clypeus) black. Scape and pedicel black; flagellum black in basal 0.3–0.6 and white in apical 0.4-0.7 except for darkened last flagellomere (Fig. B4.37). Gena from middle of eye almost to postocellar furrow white. Fore and hind wings very darkly tinted. Thorax and legs (apical articles maybe reddish brown in some specimens) black (Figs. B4.45 & B4.47). Abdomen mostly light reddish brown (Fig. B4.41); the following black or brown: tergum 1, tergum 1 and 2, side of terga 3–7, posterior margin of terga 3–6, median area of tergum 8, sterna 1 up to 1–6.

Head. Vertex densely pitted between the white genal spots (Fig. B4.47).

Thorax. Metatibia 5.0–6.5 times as long as maximum width. Metatarsomere 1 in lateral view 4.0–5.0 as long as maximum height (Fig. B4.45).

Taxonomic Notes

Many of the above synonyms are due to great color variation in females. However, when numerous females are available from the same region and even the same locality the leg and abdominal color variation is great. No geographical pattern is associated with this color variation.

Hosts and Phenology

The host range of U. cressoni is rather wide (Craighead 1950, Smith, 1979: 128). All published host records are Pinaceae, and only 2 reared and confirmed specimens were examined: Abies balsamea, A. fraseri, Larix occidentalis (2), Picea sitchensis, Pinus contorta, P. rigida, P. taeda, P. virginiana, and Pseudotsuga menziesii.

Based on 846 field-collected specimens, the earliest and latest capture dates are June 26 and September 27. The main flight period is from the second half of July to the first half of September with a peak in August.


CANADA: MB, NS, NB, ON, PI, QC, SK. USA: CO, CT, DC, FL, GA, IA, IN, MA, MD, MN, NC, NE, NJ, NY, OH, PA, SC, TN, VA, WV, WI. Urocerus cressoni, an eastern species, is known from southern Saskatchewan to Nova Scotia, and south to Florida (Lintner 1898, Rohwer 1928, Craighead 1950, Burks 1958, Burks 1967, Smith 1979) (Fig. C22.6).

Specimens studied and included for the distribution map: 1493 females and 44 males from BYUC, CNC, CUCC, CUIC, DEBU, EDUM, FRLC, GLFC. LECQ, LEMQ, MNRQ, NCSU, NFRC, UCRC, USFS–GA, and USNM.

Specimens for molecular studies: 12 specimens. See Fig. E2.4b.

CANADA. Nova Scotia: 2006, CBHR 299, 658. Ontario: 2007, SIRCA 034, 639; 2007, SIRCA 038, 639. USA. Colorado: 2005, CBHR 192, 658; 2005, CBHR 559, 658. Georgia: 200, CBHR 517, 658. Illinois: 2006, CBHR 169, 658. Indiana: 2005, CBHR 176, 658. New York: 2005, CBHR 196, 658; 2005, CBHR 200, 658; 2005, CBHR 204, 658. South Carolina: 2006, CBHR 893, 658.