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Revision of the World species of Xeris Costa (Hymenoptera: Siricidae)
CJAI 28 -- September 25, 2015
doi: 10.3752/cjai.2015.28
Henri Goulet1, Caroline Boudreault1 and Nathen M. Schiff2

9. Xeris melancholicus (Westwood)

Fig. C9.1, (female habitus); Schiff et al. 2006: 92, 93

Fig. C9.2 (male habitus)

Fig. C9.3 (live male)

Sirex melancholicus Westwood, 1874: 116, pl. XXI, fig. 8. Holotype male (OXUM), images of male prepared by James E. Hogan and sent to HG for study. Type locality “America Septentrionalis”.

Xeris melancholicus: Schiff et al. 2012.

Urocerus caudata; Cresson, 1880: 67 (not Cresson, 1865: 247–248). Synonymy by Provancher 1883: 241; Harrington, 1893: 148–149.

Xeris spectrum spectrum; Maa, 1949: 86 (not Linnaeus, 1758: 560 only for Nearctic records); Burks 1958: 17, Smith 1979: 129 (catalog); Taeger et al., 2010: 105 (in part, catalog).

Xeris spectrum; Middlekauff 1960: 70 (not Linnaeus, 1758: 560 for Nearctic records); Smith & Schiff 2002: 185.

Diagnostic combination

Among specimens with small and scattered pits between dorsoposterior edge of eye and occiput outside postocellar area and with fore wing cell C yellowish brown [melancholicus and caudatus], X. melancholicus is distinguished in most females by the sheath with basal section usually more than 0.27 times length of apical section, usually by the presence of meshes of microsculpture on laterobasal angle of cornus in dorsal view, and by abdominal tergum 9 in lateral view with meshes of microsculpture usually well impressed, with sculpticells scale-like on surface posterior to and above lateral furrow (surface thus dull). Males have a black to reddish-brown, poorly defined spot at the base of metatibia but cannot be separated from those of X. caudatus.



Color. Head black except for small white spot on gena dorsal to middle of eye; white spot usually not extending to genal ridge (Fig. B2.47); antenna black; last maxillary palpomere black (Fig. B2.47). Thorax black except for white longitudinal band extending from posterolateral to anterolateral angles including vertical portion of anterior angle, the band 0.2–0.3 times as wide as lateral 0.5 of pronotum and not extending to lateral margin of pronotum (Fig. B2.56). Legs including coxae light reddish brown (coxae very narrowly black at anterior and posterior dorsal edges) (Fig. B2.49). Fore wing clear except for lightly tinted band in apical 0.25, and on posterior corner of cells 2CU and 3CU (as in Fig. B2.67); costal cell yellowish brown (possibly bleached in old specimens) (Fig. B2.39); most of area ventral to anal cells yellowish brown; veins black or brown (including veins C and R, and base of stigma on both sides of junction with vein 1r-rs) (Fig. B2.39). Abdomen black (Fig. C9.1). Sheath with apical section black and basal section reddish brown.

Head. Distance between nearest eye edge and lateral ocellus edge about 1.1–1.5 times as long as distance between inner edges of lateral ocelli (as in Fig. C1.5). Setae on clypeus about as long as diameter of a lateral ocellus (Fig. B2.47). Eye in lateral view (N = 20) with its maximum height 1.37–1.64 times as long as its maximum length (Fig. B2.47), and maximum height of eye 0.42–0.51 times as long as maximum height of head (from transverse ridge on gena above mandible to top of head) (as in Fig. B2.8). Gena in dorsal view with maximum distance between outer edges clearly wider than maximum distance between outer edges of eyes (Fig. B2.42) (in frontal view outer edges of eyes clearly not intersecting genae) (Figs. B2.5), in lateral view with distance between outer edge of eye and genal ridge 0.48–0.61 times as long as maximum length of eye (Fig. B2.47, measurements as in Fig. B2.77), with almost no pits ventral to genal ridge, and with few small to very small pits (diameter of pit 0.05–0.15 times lateral ocellus diameter) between outer edge of eye and genal ridge (mainly near eye) (Fig. B2.47). Transverse ridge above mandible narrow, sharp and mainly smooth (Fig. B2.47). Vertex scarcely pitted and pits medium in size (pit diameter 0.2–0.3 times lateral ocellus diameter), pits present from dorsoposterior edge of eye to occiput outside postocellar area, absent on most of postocellar area (Fig. B2.42); pits scattered (small specimens) or dense (large specimens) and medium in size along median furrow, a little more widespread near lateral ocelli (Fig. B2.42).
Thorax. Pronotum in lateral view without coarse polygonal pits or with coarse polygonal pits on as much as 0.7 of posterior surface (as in Fig. B2.97). Propleuron in lateral view with small pits at base with tooth behind in posterior 0.5 and with medium polygonal pits in anterior 0.5 (as in Fig. C12.7); in ventral view with scattered to moderately dense, shallow small teeth with smooth surface in between (as in Fig. B2.22). Transcutal furrow of mesonotum clearly outlined  and finely sculptured, thus mesoscutum and axilla clearly distinct (Fig. C9.4). Fore wing in middle 0.3 of vein 2A diverging very rarely slightly (as in Fig. C11.6) to usually considerably (as in Fig. C12.6) away from wing edge, and then more (as in Fig. C11.6) or less (as in Fig. C12.6) abruptly curved away from wing edge; vein 3A absent (73%), reduced to a stump (24%), rarely extending slightly as a short nebulous vein (3%), but not extending along posterior margin of wing.

Abdomen. Tergum 9 with meshes of microsculpture on ventral half below longitudinal furrow near center clearly impressed and sculpticells slightly raised as scales, and above longitudinal furrow near center well impressed and sculpticells clearly scale-like (Fig. B2.92. insert); median basin with base (outlined by two lateral black longitudinal furrows) 0.8 times as wide as its median length, with maximum width of basin 1.6 times as wide as its median length and basin about 0.5 times as long medially as median length of cornus (Fig. C1.15, measurements as in Fig. A3.2). Cornus constricted in dorsal view, its minimum width (at constriction) about 0.8 times as wide as maximum width subapically (Fig. C1.15) and its anterolateral angle in dorsal view generally with microsculpture meshes weakly to clearly impressed near angle (Fig. B2.90, insert); with large teeth in apical 0.3 (as in Fig. B2.110). Sheath. Basal section 0.24–0.35 times as long as apical section (N = 54) (Fig. C9.1); lateral surface of apical section with well-defined ridge (as in Fig. B2.13, insert); length 1.2–1.4 times as long as fore wing length. Ovipositor. Lancet with 25–29 annuli (first 15 annuli hard to see, but still outlined; N = 14) (Fig. C9.1); junction of basal and apical sections of sheath aligned usually between 2nd and 3rd annuli, or occasionally on 3rd annulus, or on 3rd–4th annuli; major pits present on last 4–5 apical annuli before teeth annuli, and with a very small pit  on each of the 9–15 preceding annuli (as in Fig. C1.18).


Color. Head with dorsal spot behind eye similar in size to female. Coxae, tibiae (usually all tibiae) and tarsomeres 1–5 black (apical tarsomeres 3–5 or 4 and 5 sometimes brown or reddish brown in old or teneral specimens) (Fig. C9.2); femora completely or mainly reddish brown, and extreme base of tibiae in most specimens with indistinctly outlined reddish-brown spot (Figs. B2.69, C9.2 and Fig. C9.3).

Thorax. Metatibia with shallow notch on dorsal edge in basal 0.25 (Figs. B2.69 and C9.2, and tarsomeres as in Fig. B2.119).

Taxonomic notes

Initially we thought that X. caudatus was a well-defined and widespread species in North America. We had several bar coded specimens from eastern North America confirming our concept. However, it was not to remain so straight forward. A population from the Cascade Mountains, Washington, based on a rather distinct barcode relative to eastern specimens was discovered (Schiff et al. 2012). For more information see “Taxonomic notes” under X. caudatus.

Schiff et al. (2012) did not know if the eastern species was named or not. They did not assign with certainty the holotype of S. melancholicus to this species because the type locality, North America, was not informative and we did not have a good diagnostic character for distinguishing males of the western X. caudatus from those of the eastern species. In spite of this and to avoid creating a synonym, they assigned Westwood’s name, X. melancholicus, to this species rather than giving it a new name (Schiff et al. 2012).

Specimens of X. melancholicus, like X. caudatus, are quite easily distinguished from Euroasiatic species of Xeris with longitudinal white bands on the pronotum, as discussed under X. caudatus. The discussion between the Eurasian species and X. melancholicus is the same as that of X. caudatus and so is not repeated (see “Taxonomic notes” under X. caudatus). However, specimens of X. melancholicus and X. caudatus are very difficult to segregate. We succeeded in separating females only, with moderate success. The separation is based on the relative length of the apical section of the ovipositor sheath, the microsculpture type on the lateral surface of tergum 9 and on the anterolateral corner of tergum 10 (base of cornus) dorsally.

Biological notes

Males and females of X. melancholicus were observed aggregating at the highest point of Mount Rigaud, Quebec. Though mating was not observed, we assume that both sexes come together for this purpose.

Hosts and phenology

Xeris melancholicus has a wide host range (Middlekauff 1960, Stillwell 1960, Cameron 1965, Morris 1967, Kirk 1975). Based on 24 reared and confirmed specimens, all are Pinaceae: Abies balsamea (15), Larix occidentalis, Picea glauca (4), and Pinus banksiana (5).

Based on 155 field-collected specimens, the earliest and latest capture dates are June 12 and August 18. The main flight period is from the second half of June to the first half of August with a peak in the second half of July.


Canada: Alberta, Manitoba, New Brunswick, Nova Scotia, Ontario, Quebec, Saskatchewan. United States: Connecticut, Maine, Michigan, Minnesota, New York. Xeris melancholicus, a widespread species, is recorded from central Alberta to Nova Scotia, Michigan and Connecticut (see map C40.6 in Schiff et al. 2012 – note: though mentioned in the text, there are no records from BC; records from NY were accidentally omitted from the text; records from MN are new).

Specimens studied: 126 females and 44 males from CNC, CUIC, FRLC, GLFC, LECQ, LEMQ, MNRQ, NFRC, ROME, USFS–GA, USFS–MS, and USNM.

Specimens for molecular studies: 16 specimens (Schiff et al. 2012). See Fig. D1.2c. For each specimen the following is recorded: country, year, state/province, specimen code (in italics), and number of base pairs.

CANADA. Alberta: 2008, SIR 086, 576; 2008, SIR 087, 563; 2008, SIR 088, 515; 2008, SIR 089, 579; 2007, SIR 111, 658; 2007, SIR 137, 658; 2007, SIR 144, 657. Nova Scotia: 2006, CBHR 297, 658; 2005, CBHR 300, 658. Ontario: 2007, GLSIR 041, 658; 2007, GLSIR 042, 616. USA. Michigan: 2005, CBHR 203, 658. Minnesota: 2008, CBHR 1375, 658; 2008, CBHR 1461, 534; 2008, CBHR 1462, 578. New York: 2006, CBHR 603, 658.

Table of contents Abstract Introduction Materials and Methods Biology Hosts Parasitoids Morphology Key DNA References Citation Appendices PDFs