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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

Tremex fuscicornis (Fabricius)

Fig. C38.1 (female dorsal habitus)
Fig. C38.2 (female lateral habitus)
Fig. C38.3 (male dorsal habitus)
Fig. C38.4 (male lateral habitus)
Fig. C38.5 (map)

Sirex fuscicornis Fabricius, 1787: 257. Type female (ZMUC), not examined. Thomson, 1871: 326. See Smith (1978) for the synonymy. Type locality: “Halae Saxonum”.
Sirex Struthiocamelus Villers, 1789: 132–133. Taeger et al. 2010.
Sirex Camelogigas Christ, 1791: 411. Taeger et al. 2010.

Diagnostic Combination

Both sexes of Tremex fuscicornis have long setae covering the body, e.g., setae of frons in lateral view are about as long as or longer than the distance between the inner edges of the lateral ocelli. Females have the cornus in lateral view not protruded and angular along the ventral edge near its base. Males have metatarsomere 5 as long as the combined length of metatarsomere 2 + 3.



Color. Head brown or black. Antenna light reddish brown or black on middle antennomeres; maxillary palp black to reddish brown; mandible mainly black. Pronotum mainly reddish brown and black at side; propleuron black (Fig. C38.2); mesonotum black to partly black and reddish brown; mesepisternum black; metathorax black. Coxae and trochanters black; pro- and mesofemur mostly reddish brown, and metafemur mostly black; tibiae and tarsi pale yellow. Wings lightly tinted yellowish brown. Tergum 1 black, tergum 2 or 2 and 3 mostly, terga 3–8 or 4–8 at side, narrowly or broadly across base, tergum 9 across middle, and tergum 10 completely to mainly yellow, remaining surfaces black. Sterna 2–7 in black in basal 0.5 and reddish brown in apical 0.5, or completely light reddish brown. Sheath mainly reddish brown.

Head. Frons in lateral view with setae on frons as long as or longer than distance between lateral ocelli (Fig. B3.2), and with mostly contiguous and small pits (diameter about 0.3 times lateral ocellus diameter), but as a narrow band less dense on gena behind eye (Fig. B3.2). Postocellar region in frontal view scarcely elevated. Antenna clearly shorter than coastal cell length of fore wing ; flagellum slightly widened centrally, and with 10–13 flagellomeres.

Thorax. Pronotum in dorsal view with numerous coarse teeth over surface. Mesonotum densely (pits 0.3–0.5 pit diameter apart) and moderately pitted on central portion. Metatarsomere 2 in lateral view with dorsal margin almost straight, about 3.0 times as long as high (Fig. B3.8), and tarsal pad 0.8 as long as its ventral length. Fore wing with length of cell 2R1 1.2–1.5 times as long as length of cell 3R1.

Abdomen. Setae long and few on median region of terga 1, 5 and 6, more widespread on posterior half of tergum 7 and posterior 0.7 of tergum 8 and laterally on terga 1–9, dense only medially on tergum 1, scattered elsewhere (distance about as far apart as length of setae). Tergum 9 laterally with surface anterior to each seta markedly elevated as a tooth (pit coarsely outlined), and very close or fused to tooth (Fig. B3.6). Median basin of tergum 9 flat, 1.4–1.6 as wide as long, base (delimited by small longitudinal furrows) about 0.9 times as long as median length, with small teeth present posterolaterally, each tooth with small seta. Tergum 10 in dorsal view 1.1–1.2 times as long as median length of median basin, with few teeth over dorsal surface and along lateral edges in apical half, and without round angular projection in basal 0.3 laterally (best seen in lateral view) (Fig. B3.4). Sheath. Basal section 1.3–1.4 times as long as apical section. Apical section about 0.5 times as long as fore wing length. Ovipositor. Lancet with about 12 annuli, and with annuli outline only under apical section of sheath. Pitted section 0.5–0.6 times as long as length of apical section of sheath; annulus 1 outlined and without pit, last annulus before teeth annuli without pit, preceding 6 annuli each with a clearly defined pit, and each pit about 0.25 times as long as segment length; first tooth annulus with a long narrow impression with a double row of sensilla.


Color. Coxae and metafemur (except extreme base) black, tibiae, and tarsi of fore and middle legs reddish brown. Abdomen mainly black

Head. Antenna almost thread-like and clearly shorter than costal cell of fore wing, and middle flagellomeres about 2.0 times as long as wide.

Thorax. Metatibia in lateral view about 4.5 times as long as its maximum width and in cross section about 1.5 times as high as its maximum ventral width. Metatarsomere 1 about 3.5 times as long as high. Metatarsomere 5 as long as length of metatarsomeres 2 + 3 (Fig. B3.10).

Abdomen. Sterna completely and quite densely pitted. Sternum 8 with apical edge widely (about half of the width of apical edge) deeply indented.

Taxonomic Notes

Illustrations of the holotype were examined and match closely our specimens from Europe. We have seen two specimens from Chile and they seem to match closely the European specimens we examined. Although a large number of Tremex species exist in China, it is possible that the European species may be different in China (Stephan Blank, personal communication). For the purposes of this paper we accept the identity of Chilean specimens as the Palaearctic T. fuscicornis.

Biological Notes

Information on the biology of Tremex fuscicornis and its associated fungus were published by Palma et al. (2005), Parra (2007), and Pazoutová and Srutka (2007).


In Chile, Tremex fuscicornis is most destructive to poplar (Populus nigra), but it is also recorded from Robinia pseudoacacia and Acer negundo (Baldini 2002; Palma et al. 2005; Parra 2007).


CHILE: Near Santiago: Provincia de Aconcagua, V Región (Palma et al. 2007); Región Metropolitana (Baldini 2002); Región Valparaiso (Parra 2007), Región: R. M., Communa: NOS, Col., César Hernández, Fecha: 17/03.01 (1 F; 1 M; OSAC). Tremex fuscicornis is a Palaearctic species known from Europe to Japan. It was accidentally introduced into central Chile (Fig. C38.5) and was first reported by Baldini (2002). It apparently entered the country in wooden crates infested with larvae from China (Baldini 2002; Pažoutová and Šrǔtka 2007).

Specimens studied (two specimens from Chile and a few specimens from Europe and Asia) are included for the distribution maps: 11 females and 4 males from CNC, OSAC and USNM.

Specimens for molecular studies: 7 specimens. See Fig. E2.2.

CHINA: 2006, CBHR 387, 658; 2006, CBHR 391, 658; 2006, CBHR 392, 658; 2006, [associated pre-adult], CBHR 394, 658; 2006, [associated pre-adult], CBHR 395, 658; 2007, CBHR 1201, 658; 2007, CBHR 1202, 658.