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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

Xeris indecisus (MacGillivray) species re-instated

Fig. C42.1, Schiff et al. 2006: 84, 85 (female with reddish brown abdomen, habitus)
Fig. C42.2, Schiff et al. 2006: 95, 96 (female with black abdomen, habitus)
Fig. C42.3, Schiff et al. 2006: 83 (male with reddish brown abdomen, habitus)
Fig. C42.4, Schiff et al. 2006: 91 (male with black abdomen, habitus)
Fig. C39.1 (live female with dark abdomen)
Fig. C42.5 (live male with dark abdomen)
Fig. C42.6 (map)

Urocerus indecisus MacGillivray, 1893: 243. Holotype male (INHS, Webb 1980), not examined. Type locality: near Olympia, Washington.
Xeris morrisoni Bradley, 1913: 24 (not Cresson, 1880: 35); accepted by Ries 1951: 84, Middlekauff 1960: 69.
Xeris morrisoni indecisus; Maa, 1949: 85 (change in combination and rank); accepted by Burks 1958: 17, Smith 1979: 129.
Xeris spectrum townesi Maa, 1949: 88. Holotype female (USNM), examined by DRS and HG. Burks 1958: 17, Burks 1967: 27, Smith 1979: 129. NEW SYNONYM. Type locality: “Hoquiam [Washington]”.
Xeris spectrum Middlekauff 1960: 70 (in part) (not Linnaeus, 1758: 560).

Diagnostic Combination

Among adults without a longitudinal band on the lateral margin of the pronotum [morrisoni, tarsalis and tropicalis], both sexes of X. indecisus are recognized by the wide gena (in frontal view maximum width between the outer edges of eyes clearly less than maximum width between genae), and the narrow, sharp and mainly smooth transverse ridge above the mandible. Females have completely light reddish brown femora. Males have the width of the gena between the genal ridge and the outer edge of eye generally more than half as wide as the maximum eye length.



Color. Head black except for large white spot on gena dorsal to middle of eye extending down to genal ridge (Fig. B5.19); flagellum black but reddish brown on 8–12 apical flagellomeres (black abdomen form) (Fig. B5.49), or completely light reddish brown (reddish brown abdomen form, but unusually also for the black abdomen form) (Fig. B5.50). Thorax completely black or with small to large white spot present on vertical surface near anterolateral angle of pronotum (spot very narrow if visible in dorsal view) (Fig. B5.38). Legs light reddish brown except for coxae; coxae almost all light reddish brown except on surface at dorsal angle (especially in specimen with reddish brown abdomen) to brown or black with reddish brown apex (Fig. B5.38). Fore and hind wings tinted very light brown but clearly darker in cells 1R1, 1M and 2CU (almost completely clear except for a dark band before stigma and somewhat darkened in apical 0.25 in old preserved specimens) or, in southwestern United States completely darkly tinted (Fig. B5.16); costal cell brown and most of surface behind anal cells yellowish brown; veins dark brown or black (including veins C and R, and vein 1r-rs near junction with stigma). Abdomen segments 1 or 1 and 2 black, and segments 2–10 or 3–10 reddish brown (pale form) (Fig. B5.46), or abdomen completely black (dark form, not found in southwestern United States) (Fig. B5.47). Sheath with apical section black and basal section reddish brown.

Head. Eye in lateral view (20 specimens measured) with maximum height 1.36–1.66 times as long as maximum length, and maximum height of eye 0.42–0.50 times as long as maximum height of head (from transverse ridge on gena above mandible to top of head) (as in Fig. B5.7). Gena in dorsal view with maximum distance between outer edges clearly wider than maximum distance between outer edges of eyes (in frontal view outer edges of eyes clearly not intersecting genae) and in lateral view distance between outer edge of eye and genal ridge 0.50–0.64 as long as maximum length of eye (Fig. B5.27). Transverse ridge above mandible narrow, sharp and mainly smooth (Fig. B5.21). Head in dorsal view with pits restricted to vertex (quite densely pitted from dorsoposterior edge of eye to occiput) and postocellar area (medially and a little more widespread near lateral ocelli) (Fig. B5.33); in lateral view pits almost absent on gena ventral to genal ridge (Fig. B5.19), and pits scattered (mainly near eye) and small (diameter of pit 0.2–0.3 that of ocellus) between outer edge of eye and genal ridge (Fig. B5.19).

Thorax. Fore wing vein 3A absent (81%), reduced to a stump (18%), or rarely extending slightly as a nebulous vein (1%), but not extending along posterior margin of wing.

Abdomen. Median basin of tergum 9 with base (outlined by two lateral black longitudinal furrows) 0.7 times as wide as median length, with maximum width of basin 1.3 times as wide as median length, and basin 0.5 times as long medially as median length of cornus. Cornus constricted in dorsal view, its minimum width (at constriction) 0.8 times as wide as maximum width of cornus subapically. Sheath. Length 1.2–1.5 times as long as fore wing length; basal section 0.20–0.31 times as long as apical section (Fig. B5.25); lateral surface of apical section with well defined ridge (as in Fig. B5.13, see insert). Ovipositor. Lancet with 25–33 annuli (first 15 annuli difficult to see, but still outlined); junction of basal and apical sections of sheath aligned between 2nd and 3rd, at 3rd, or between 3rd and 4th annuli; major pits present on last 4–6 apical annuli before teeth annuli, and at most 6 preceding annuli with a very small pit.


Color. Antenna, coxae, femora (at least metafemur mostly black, but pro– and mesofemur black in most specimens to mainly reddish brown), tibiae (except for brown at very base in some specimens) and tarsi (except reddish brown tarsomeres 3–5 or 4 and 5) black. Pronotum completely black, or vertical surface in front of dorsolateral angle with small to large white spot; dorsal surface of pronotum black or with white spot extending at most toward posterolateral angle. Abdomen black on segments 1 and 2 and laterally on terga 3–8, and reddish brown elsewhere (pale form), or completely black (dark form).

Thorax. Metatibia with shallow notch on dorsal edge in basal 0.25 (Fig. B5.40).

Taxonomic Notes

The holotype of U. indecisus was not examined. The description (especially the femora and pronotal color pattern) matches our concept for this species.

Xeris spectrum townesi specimens share with X. indecisus the large spot size on the gena, and the denser pits on the gena and vertex; females share the flagellum and the pronotum color, and males share the pronotum and metafemur color. Males of the pale abdomen form match the description of the type of Xeris indecisus, and females of the black abdomen form match Xeris spectrum townesi. Both sexes of both color forms are easily associated. Both color forms have the same range except from Utah and the Black Hills of South Dakota and south where only the pale color form occurs), and adults are often found together.

The pale abdomen and dark abdomen forms were classified until now as two species (Maa 1949, Ries 1951, Middlekauff 1960, Smith 1979). Information from morphology and DNA barcoding confirms that the two discrete color forms of both sexes belong to one species. Therefore, these color forms are treated here as one species.

Xeris indecisus has been ranked as a subspecies of X. morrisoni (Maa 1949, Ries 1951, Middlekauff 1960, Smith 1979). However, the information from morphology and DNA barcoding confirms that the two taxa are different. Moreover, the two species are sympatric in Colorado and females are easily distinguished on color pattern. Therefore, we consider X. indecisus and X. morrisoni as specifically distinct.

Geographical Variation

Adults of X. indecisus have two distinct color forms: the abdomen is either mainly reddish brown or completely black. Both color forms are known from coastal and interior regions of British Columbia south to California. However, the reddish brown abdomen form is the only form recorded in southwestern United States (Arizona, Colorado, Nevada, South Dakota and Utah). Dark winged specimens are recorded from the latter states. Wings less darkly tinted where both color forms occur.

Less obvious are variations in ovipositor length. The basal section of the sheath is proportional to body size, but the apical section is not. We calculated the ratio between the basal and apical section as a general measure of relative size for the ovipositor, based on 72 specimens. In South Dakota, females (18) have generally a short ovipositor with a ratio of basal to apical sections of 0.24–0.31 (mean = 0.27). At the other extreme, specimens (10) from Lake Tahoe, California, have a ratio of 0.20–0.25 (mean = 0.23). In Oregon and British Columbia, females (44) have ratios of 0.20– 0.32 (average 0.25). Therefore specimens from California have a relatively longer apical section of the sheath than most of specimens from elsewhere. DNA barcodes based on 21 specimens from regions with long and short ovipositors does not segregate specimens into two groups. We see no reasons to recognize subspecies.

Hosts and Phenology

Xeris indecisus has a wide host range (Bedard 1938 – under X. morrisoni, Cameron 1965, Morris 1967). Based on 121 reared and confirmed specimens, all but one host are Pinaceae: Abies sp. (13), A. concolor (17), A. grandis (10), A. lasiocarpa (8), A. magnifica, Larix occidentalis (12), Picea sp. (1), P. sitchensis (10), Pinus contorta (2), P. ponderosa, Pseudotsuga menziesii (28), and Tsuga heterophylla (20). There is one record from Calocedrus decurrens (Cupressaceae).

Based on 24 field-collected specimens, the earliest and latest capture dates are May 18 and September 11 The main flight period is from the first half of June to the first half of September.


CANADA: BC. USA: CA, CO, ID, MT, NV, OR, SD, UT, WA. Xeris indecisus, a widespread western species in forested regions, is recorded from British Columbia to California and Colorado (Burks 1967, Cameron 1965, Smith 1979) (Fig. C42.6). The specimens of X. indecisus recorded by Burks (1967) under X. spectrum townesi from Arizona needs confirmation as they could be specimens of X. chiricahua. One female was intercepted in Osaka, Japan, from United States (Okutani 1965) and we have seen a female intercepted in New Zealand (FRNZ and PANZ).

Specimens studied and included for distribution map: 232 females and 113 males BYUC, CFIA, CNC, DEBU, EDUM, OSAC, PFRC, UASM, UCRC, USFS–GA, USFS–MS, and USNM.

Specimens for molecular studies: 21 specimens. See Fig. E2.3.

CANADA. British Columbia: 2006, CBHR 418, 658; 2006, CBHR 419, 658; 2004, SIRCA 092, 658; 2004, SIRCA 093, 658. USA. California: 1999, CBHR 98, 658; 2007, CNCS 1076, 600; 2007, CNCS 1077, 576; 2007, CNCS 1078, 654. Colorado: 2005, CBHR 189, 658. Oregon: 1999, CBHR 108, 658; 2006, CBHR 385, 658; 2006, CBHR 1078, 658; 2007, CNCS 1080, 615. Washington: 2005, CBHR 215, 658; 2005, CBHR 216, 658; 2005, CBHR 228, 658; 2005, CBHR 235, 658; 2005, CBHR 239, 658; 2005, CBHR 241, 658; 2005, CBHR 254, 658; 2008, CBHR 1310, 658.