Fig. C8.1 (female habitus)
Fig. C8.2 (male habitus)
Fig. C4.4 (map)
Among females with a completely light reddish brown metafemur, short metatarsomere 2 (tarsomere 1.5-3.0 times as long as high), black abdomen, and long tarsal pad (length of pad 0.7–0.8 as long as ventral length of tarsomere) [abietinus, nitidus, and varipes], those of S. cyaneus are recognized by the much very small pits at the middle of the lancet (pit length 0.0–0.13 times as long as length of annulus), length of annulus 10 1.33–1.82 as long as height of ovipositor (lance + lancet) at this annulus, and the lack of pits in basal 6–9 annuli of the ovipositor. Among males with a reddish brown metafemur and mainly black metatibia [abietinus, nitidus, noctilio and varipes], those of S. cyaneus are recognized by the completely light reddish brown mesotibia and mesotarsus, the moderately large pits on the gena and the vertex (diameter of pit 0.25–0.4 that of lateral ocellus), and the narrow pale base of the metatibia (spot extending slightly beyond minimum constricted portion and as long as or slightly longer than wide).
Adults of S. cyaneus are extremely similar to those of S. abietinus. If the male is from east of the Rocky Mountains within the range of Abies balsamea, it is likely this species, but outside this range it will likely be those of S. nitidus.
Color. Body, antenna (less than 3% of specimens with flagellomeres 1 or 1 and 2 brown; only one specimen with flagellomeres 1–4 light reddish brown), and palps black with dark blue metallic reflections. Coxae black; femora (except brown base), tibiae, and tarsi (apical half of tarsomere 5 usually darker but not dark brown or black (as in Fig. B2.60)) light reddish brown. Fore wing mainly clear, at most light yellowish brown behind stigma.
Head. Gena with pits 2.0–6.0 pit diameters apart and mainly absent centrally behind eye; vertex and postocellar area with pits 0.0–2.0 pit diameters apart (as in Fig. B2.62), and each pit diameter 0.15–0.2 that of lateral ocellus.
Thorax. Mesoscutum with coarse, net like–pits in posteror 0.6 of median area (as in Fig. B2.65). Metatarsomere 2 in lateral view 2.3–2.8 times as long as high, and length 1.1–1.2 times length of tarsomeres 3 + 4; tarsal pad 0.8–0.9 times as long as ventral length of tarsomere (as in Fig. B2.67). Fore wing vein 3A absent.
Abdomen. Median basin of tergum 9 with basal width 0.9–1.3 times as long as median length, maximum width 1.1–1.5 times as long as median length, and median length 0.55–0.65 times as long as cornus length (Fig. B2.88). Cornus in dorsal view short, with edges straight to slightly angular midway; its median length 1.05–1.3 times as long as maximum width of abdomen at junction of terga 9 and 10 (Fig. B2.88). Sheath. Length 0.7–0.87 times fore wing length, basal section 0.87–1.12 times as long as apical section. Ovipositor. Lancet with 29–33 annuli (basal annuli hardly outlined and very difficult to see); junction of basal and apical section of sheath aligned between 9th and 10th or 10th and 11th annuli, with 16–20 pits beginning with annuli 8–10 (Fig. B2.84, base). Pits near middle annuli or area at base of apical section of sheath 0.0–0.12 times as long as an annulus (pits gradually and markedly decreasing in size toward base and disappearing before any of annuli 7–11), 0.07–0.25 times as high as lancet height in lateral view, and about 1.0–1.6 times as long as high (Fig. B2.86); annulus 10 length/ovipositor diameter (lance + lancet) 1.33–1.82 (based on 29 specimens) (Fig. B2.86). Last 3-4 annuli before teeth annuli as well as first tooth annulus with ridge on ventral edge of pit. Edge of apical 5-7 annuli before teeth annuli extending as ridge to ventral edge of lancet.
Color. Head and thorax black with dark blue metallic reflections. Coxae, metatibia (except extreme base), and metatarsomeres 1–3 black; femora, tibiae, and tarsus of fore and middle legs light reddish brown (Fig. B2.132). Fore wing clear. Abdomen with segments 1 and 2 or 1–3 black, segments 3–7 or 4–7 light reddish brown, and segment 8 black, rarely light reddish brown (Fig. B2.133); sternum 8 and 9 black or completely reddish brown (only specimens from Alberta).
Thorax. Metatibia 4.2–4.6 times as long as maximum width. Metatarsomere 1 in lateral view 3.2–3.6 times as long as maximum height.
Much of the North American literature under S. cyaneus or S. juvencus is very confusing because up to five species fall under these traditional names (Slosson 1895, Blackman and Stage 1918, Essig 1926, Rohwer 1928, Middlekauff 1960, Benson 1963, Cameron 1965, Okutani 1965, Smith and Schiff 2002, Schiff et al. 2006).
Females of S. cyaneus have commonly been confused with females of the European “S. cyaneus” (identified here as S. torvus M. Harris, see Chapter D. Additional Notes) and S. juvencus because the whereabouts of the Fabricius type of S. cyaneus was unknown. Its discovery in HMUG clarifies the name used for several European and American species. Sirex cyaneus is distinguished from all European species (S. juvencus, S. torvus, and S. atricornis) by the absence of pits and annuli in the basal 0.4 of the ovipositor. The following character states also distinguish S. cyaneus from S. torvus: in both sexes of S. cyaneus the pits on the gena and vertex are moderate in size (smaller in S. torvus); in females of S. cyaneus there are no pits in the basal annuli of the ovipositor (pits start on ovipositor annulus 2 in S. torvus) and, on average, the apical section the sheath is equal to the basal section (apical section longer than basal section in S. torvus); in males of S. cyaneus (except in Alberta) the abdominal apex is black (reddish brown in S. torvus) and (except in a very few specimens from Alberta) the mesotibia and mesotarsus are completely light reddish brown (widely black mesotibia, except at base, and mesotarsomeres 1–3 in S. torvus). Sirex cyaneus has even been considered as a subspecies of S. juvencus. Adults of S. juvencus are easily distinguished from those of S. cyaneus by antennal color pattern and ovipositor pit development.
Sirex abbotii and S. hirsutus have been assigned traditionally to S. cyaneus. The holotype male (from coastal Georgia or southeastern USA) of S. abbotii matches males of S. cyaneus in color pattern. In the southern Appalachian Mountains, Abies fraseri is the only host for S. cyaneus. Abies fraseri grows only at high elevations. The holotype could have arrived in coastal Georgia (where A. fraseri is absent) with logs harvested in the Appalachian Mountains in westernmost Georgia or South Carolina. The holotype of S. hirsutus is not a Nearctic species as it is a typical specimen of S. juvencus (see Chapter D. Additional Notes about its synonymy). So the holotype is probably an intercepted specimen from Europe.
Where the ranges overlap, females of S. cyaneus could be confused only with S. nitidus and S. noctilio females. Ovipositor pit development distinguishes S. cyaneus from these two species. In addition, both sexes of S. cyaneus are easily distinguished from those of S. noctilio on puncture size on the vertex and pit development on the mesoscutum, and females of S. cyaneus are distinguished by the long tarsal pad of metatarsomere 2 and very small pits near the middle of the ovipositor.
Outside its range S. cyaneus could be confused with S. abietinus, a species found from the Rocky Mountains and westward. The S. cyaneus range extends as far as west of Lesser Slave Lake, Alberta. The two species are probably allopatric like their main hosts, various species of Abies. There is a gap between A. balsamea, an eastern species, and A. lasiocarpa, a western species, in western Alberta. In S. cyaneus, females have annulus 10 relatively short compared to ovipositor diameter, and, commonly, a relatively thin, short cornus (relatively long annulus and a thick cornus in S. abietinus); males (only those at least from Manitoba and eastward) have black sterna 8 and 9 (in most specimens tergum 8 is completely black) (completely light reddish brown apical abdominal segments in S. abietinus). The information from morphology and DNA barcoding shows a difference of almost 10.6% in base pairs between S. cyaneus and S. abietinus. Despite their great similarity, the two taxa are considered as specifically distinct.
Stillwell (1966) published a fine study on the biology S. cyaneus (under the name S. juvencus – 800 specimens of this study are in CNC and all are S. cyaneus). Adults were reared from weakened Abies balsamea collected throughout New Brunswick and Nova Scotia.
Females oviposit in dead and dying firs, but they could be induced to oviposit in healthy logs. Males emerge first, but continue to emerge throughout the summer. On the day of emergence, females start to oviposit. Oviposition lasts from 4–20 minutes (most last 8–10 minutes). The ovipositor penetrates at about right angle to the surface to a depth of 2–10 mm. Generally, each female lays one to three eggs as the ovipositor is withdrawn. The eggs are about 1 mm long and usually overwinter or hatch in late summer. Larvae overwinter in the first or second instar. The first instar is usually within the oviposition hole, but the second instar larva bores at about a right angle to the oviposition hole. Larvae molt 5–11 times, based on exuviae that are packed in the frass at intervals within each gallery. Most larvae stay within the first 4 cm of the log surface and the length of the galleries vary from 5–15 cm. The pupae are in a chamber usually 2 cm below the surface. The prepupa lasts 4–6 weeks and the pupal stage 2–3 weeks. Most life cycles last two years, but some may last three years. Unmated females produce males only, mated females produce both sexes.
A mycangium is a special organ that carries oidia (kind of fungal conidia). Two mycangia are found at the base of the ovipositor. In most instances oidia are carried in them. Several kinds of fungi grow in a log, but only one, Amylostereum chailletii (in Stillwell’s paper, this species is under the genus Stereum) is carried by females of S. cyaneus. The oidia are deposited on the end of each egg at oviposition time and are also found along the oviposition hole. The larva at hatching time has plenty of this fungus to eat. Without the fungus the larvae dies at the first instar. Female larvae carry the fungus in a paired organ called the hypopleural organ. This organ is found in the fold between the first and the second abdominal segments. Following a molt, the fungal oidia remain in the exuvia and the female larvae must pick the fungus again to fill the new hypopleural organ. The female prepupae enclose the fungal oidia in wax-like plates.
The host range of S. cyaneus is mainly restricted to species of Abies (99% of the reared specimens). Based on 1103 reared and confirmed specimens, all recorded hosts are Pinaceae: Abies sp. (38), Abies balsamea (932), A. fraseri (16, Kirk 1974), Larix sp. (5), Picea glauca (10), P. mariana (1), and Pinus strobus (1), P. elliottii (Kirk, 1974) under S. abbotii (see S. cyaneus synonymy), is record of a specimen taken outside the range of S. cyaneus). Verified published records: (Stillwell 1960, Stillwell 1966, Amman 1969, Kirk 1974); unverified published records: Belyea (1952).
Based on 675 field-collected and reared (under natural conditions) specimens, the earliest and latest capture dates are July 2 and October 3. The main flight period is from the second half of July to the first half of September with a peak in second half of August.
CANADA: AB, MB, NB, NL, NS, ON, QC, SK. USA: ME, MI, MN, NC, NH, WV. Sirex cyaneus is recorded from western Alberta to Newfoundland south to the Great Smoky Mountains (Fig. C4.4). We have seen many intercepted specimens from New Zealand (FRNZ).
Specimens studied and included for range map: 484 females and 933 males from CASS, CNC, CUIC, DEBU, FRLC, GLFC, LECQ, LEMQ, NFRC, NFRN, and USNM.
Specimens for molecular studies: 11 specimens. See Fig. E2.5d.
CANADA. Alberta: 2008, CNCS 1030, 598; 2008, CNCS 1031, 575; 2008, CNCS 1032, 575; 2008, CNCS 1033, 580; 2008, CNCS 1034, 580; 2008, CNCS 1035, 577; 2008, CNCS 1036, 587. New Brunswick: year unknown, SIRCA 043, 594; 2007, SIRCA 044, 613. USA. New York: 2006, CBHR 610, 658. Washington: 2007, CBHR 1327, 628.