Taracus gertschi Goodnight & Goodnight 1942

Shear, William A. & Warfel, Joseph G., 2016, The harvestman genus Taracus Simon 1879, and the new genus Oskoron (Opiliones: Ischyropsalidoidea: Taracidae), Zootaxa 4180 (1), pp. 1-71 : 30-32

Taracus gertschi Goodnight & Goodnight 1942

Figs. 37–45 , Map 5

Taracus gertschi Goodnight & Goodnight 1942:1 . Cokendolpher & Lee 1993:6 (list). Schönhofer 2013:21 (list).

Type. Juvenile holotype in AMNH, from Rose Lake , Kootenai Co. , Idaho (examined 2012), type locality here corrected ( ICZN Rec. 76A.2). In the original description, Goodnight and Goodnight (1942) gave the type locality as “eastern Oregon,” but the type itself is labeled, in Goodnight’s distinctive handwriting, as being from Rose Lake , Idaho ; the only community so named in Idaho is in Kootenai Co., southwest of Coeur d’Alene . This northern Idaho locality is a considerable distance from any point in “eastern Oregon . ” Taracus gertschi does in fact occur in eastern Oregon, but that is not the correct type locality. The type specimen is immature, though an attempt had been made at one time to extract genitalia. Our surmise, based on its size and general appearance, is that it is a penultimate or antepenultimate female. The type matches juvenile and mature specimens from the localities listed below, and this, together with geography, supports the identity of this species.

Diagnosis. Taracus gertschi is closest in general appearance to T. pallipes , but is smaller, with shorter legs, and distinct from pallipes in that the females have more distinct scutum laminatum, with extensive but separate central tergites on each of the abdominal segments instead of just the first two or three. The usual small, black setae of the abdomen are not set on distinct conical tubercles as in species of Oskoron , though apart from those on the tergites they are found on sclerotized plaques. In males, scutum parvum is more extensive than in pallipes , with heavier sclerotization, and the seta-bearing plaques are far less prominent; in fact the scutum can appear almost smooth. In addition, the chelicerae of gertschi have more and larger seta-tipped tubercles on the basal article, and those of the male are stouter than in pallipes . The male penis is distinctive. A character that appears unique to T. gertschi is the presence of prominent slit sense organs anterolateral to the ocularium on each side.

Description. Male from Glacier National Park, Montana: Total length, 3.67 mm. Carapace chestnut brown, with four darker “hash marks” on either side of ocularium, all carapace edges well-defined, anterior and posterior margined; strongly domed, anteriorly with three or four prominent setae; midline sulcus extends from anterior margin to ocularium. Ocularium somewhat longer than wide, rounded, few scarcely detectable setae above each eye; eyes small, black, ringed with black pigment. Prominent slit sense organ anterolateral to ocularium on each side. Metapelitidium well sclerotized but clearly distinct from carapace, without setae; sensory cone white, tipped brown, acute, arising from white socket-like space entirely enclosed by metapeltidium. Abdomen with scutum parvum, scutum anteriorly margined, lateral margins distinct; scutum irregularly set with small black setae slightly raised on low plaques, none distinctly larger than others. Unsclerotized sides of abdomen with similar setae. Ventrally, coxae pale yellowish, unspotted. Palpal coxae with numerous stout setae on distinct tubercles, leg coxae with strong, black setae, not on tubercles. No indication of thoracic sternum. Genital operculum apically rounded, heavily setose, pale yellowish tan, unspotted. Anterior abdominal sternites not sclerotized, posterior sternites with central sclerotized patches; with scattered black setae.

Chelicerae ( Fig. 45 ) 8.16 mm long, black. Basal article 3.67 mm long, 0.49 mm wide (L/W = 7.49); second article 4.49 mm long, 0.71 mm wide (L/W = 6.32). Basal article with prominent mediobasal knob, with long, setatipped tubercles numerous, diminishing only slightly distally; second article with more numerous, but more rounded seta-tipped tubercles ranged in about four or five irregular rows, tubercles densely spaced over anterior face of article to base of fixed finger. Fixed and movable fingers with paired, articulating triangular teeth, narrow, acute tips of fingers cross each other at rest.

Palpi ( Fig. 38 ) yellowish white, shaded darker distally, total length 8.16 mm, slender; trochanter with five or more rather low, seta-tipped tubercles, femur with regularly spaced slender setae, not set on tubercles. Patella not swollen. Lengths of articles as given in Table 6 . Legs long, thin; yellowish white, unspotted. Autospasy sutures of femora distinct on all legs. Tibiae without false articulations, metatarsal false articulations (4?), 17, 0, 0 respectively (false articulations, if present on first leg, poorly indicated). Total lengths in mm of legs 1–4: 11.24, 17.20, 10.73, 14.21. Measurements of leg articles given in Table 6 .

Penis ( Figs. 39, 40 ) 1.75 mm long, 0.30 mm wide (L/W =5.83), sides of shaft straight; glans slightly swollen, abruptly tapering to narrow, acute aculeus; aculeus with subtending crown of setae incomplete ventrally; sparsely setose dorsally; shaft with few scattered small setae distally.

Female from Glacier National Park, Montana: Total length, 4.67 mm. Carapace dark brown to black, lighter areas behind and beside ocularium with “hash marks.“ Metapeltidium well sclerotized, without setae; sensory cone entirely enclosed by metapeltidium. Abdomen pale tan, scutum laminatum present, tergites irregularly formed from fusion of abdominal plaques, lacking setae except around anterior and posterior edges, surrounded by densely but irregularly arranged raised seta-bearing plaques of various sizes, generally smaller laterally ( Figs. 41, 42 ).

Chelicerae ( Figs. 43, 44 ) black, 10.00 mm long; cheliceral basal article 4.50 mm long, 0.60 mm wide (L/W = 7.5); second article 5.50 mm long, 0.80 mm wide (L/W = 6.9). Total length of palpus ( Fig. 37 ), 9.04 mm; femoral setae not on tubercles. Total lengths in mm of legs 1–4: 11.63, 18.19, 11.41, 16.25; lengths of leg and palpal articles as given in Table 7 . Second leg metatarsus with 11 false articulations, 5 poorly developed false articulations in first metatarsus. Ovipositor typical. Other characters as in male.

Distribution. Unless otherwise noted, all specimens CNC. CANADA: ALBERTA: Chinook Lake, N49°40’, W114°30’, 4800’ asl, 26 July 1988, D. J. Buckle, Ƌ. Waterton Lakes National Park, Crandell Lake Trail, N5440772, E0283451, 1602 m asl, m 18 August 2002, J. & K. Hancock, juv, N49°03’00”, W113°44’11”, 5200’ asl, 29 August–10 September 2000, E. Kinsella, ƋƋ. Waterton Lakes National Park (no further data), 22 October 2005, J. Hancock, m. BRITISH COLUMBIA: 48 mi SE Elko, Lodgepole Pine Rd., 10 km S of Hwy.3, 2.2 km N of Ram Creek Rd., N49°19’48.9”, W114°56’34”, 25 August 2007, R. M. Shelley, M. F. Medrano, Ƌ (WAS). 18 mi E Creston, 20 October 1988, D. W. Knight, Ƌ. UNITED STATES: IDAHO: Boise Co.: 10 mi NE Idaho City, 20 July 1983, “EEL”, m. Shoshone Co.: headwaters of Merry Creek, along Merry Creek Rd., N47°04.589’, W116°08.667’, 4100’ asl, 3 July2005, W. Leonard, C. Richart, 2 juvs. (WAS); Hobo Cedar Grove Botanical Area, N47°05.158’, W116°06.770’, 4350’ asl, 3 July 2005, W. Leonard, C. Richart, juv (WAS). MONTANA: Flathead Co., Glacier National Park, 1988 Red Bench Fire Study Site 1, N48°51.06’,W114°21.28, 3760’ asl, 22 July–12 August1991, D.&M. Ivie, Ƌ, Site 8, N48°46.06’, W114°16.47’, 3666’ asl, 23 July–13 August 1991, D.&M. Ivie, Ƌ; Site 12, N48°48.02,W114°13.52, 3660’ asl, 23 July–13 August, 20 August–10 September 1991, D.&M. Ivie, 6 mm, f, 3 juvs; Site 14, N48°44.39’, W114°14.57’, 3520’ asl, 26 June–12 July 1991, D.&M. Ivie, juvs., 21 August–11 September 1991, D.&M. Ivie, m, Site 16, N48°51.17’, W114°20.70’, 3760’ asl, 23 July–12 August 1991, D.&M Ivie, 2 juvs; Site 17, N48°49.41’, W114°17.29’, 4096’ asl, 22 July–12 August, 19 August–9 September 1991, D.&M. Ivie, ƋƋ; Site 23, N48°41.53’, W114°10.60’, 3560’ asl, 21 August–11 September 1991, D.&M. Ivie, ƋƋ. Mineral Co.: St. Regis, 23 September 1950, V. Roth, Ƌ (CAS). OREGON: Baker Co.: west of Anthony Lakes Ski Area, Wallowa Whitman National Forest, 7000’ asl, 14 August 1972, T. Briggs, R. Lem, m (CAS); 1.8 mi W of Anthony Lakes Ski Area, same data, ♀ (CAS); 5.4 mi E of Anthony Lakes Ski Area, 5,200’ asl, same data, Ƌ ♀♀ (CAS); Anthony Lake, 19 July 1953, V. Roth, juv. (CAS). Grant Co.: Dixie Pass, 5000’ asl, no date, T. Briggs, Ƌ (CAS). Wallowa Co.: Wallowa Mtns., west fork Wallowa River, 2070–2130 m asl, stop #82-16, 10 July 1982, D. H. Kavanaugh, Ƌ (penult), ♀ ♀ (CAS); WASHINGTON: Stevens Co.: Cedar Lake, W117.36, N48.55, 10 September 1963, J. & W. Ivie, Ƌ ♀♀ (AMNH). Whitman Co.: Elberton, 3 July 1979, C. R. Knight, Ƌ; Kamiak Butte State Park, 10 August 1967, A. Jung, ♀ (CAS); Tekoa Mountain, 3940’ asl, 6 pitfalls in forest, 47.259°N, 117.088°W, 9 October 1994 – 7 July 1995, J. Bergdahl, Ƌ ♀ (UWBM); Kamiak Butte, 3040’ asl, 8 pitfalls in forest, 46.867°N, 117.155°W, 4 June–26 August 1994, J. Bergdahl, juvs (UWBM).

T. gertschi occurs in northern Idaho, adjacent eastern Washington and Oregon, western Montana, the southeast corner of British Columbia and in Waterton Glacier International Peace Park in Alberta and Montana . It probably has a somewhat wider range in the northern Rocky Mountains, as indicated by the record from Boise Co , Idaho, and juvenile specimens possibly this species in AMNH.

Notes. Goodnight & Goodnight (1948) pointed out in the original description of the juvenile holotype what appeared to them to be a diagnostic character: immediately behind the metapeltidial cone, on the first abdominal region, are two closely set, prominent, white knobs with acute tips. Though Goodnight and Goodnight illustrated, but do not mention it, these knobs occur near the midline of each of the abdominal segments of the holotype. Examination of additional immature specimens from the range of this species show that this “character” is due to shrinkage of the abdomen, either before or after preservation. Mature females and juveniles of T. gertschi have scutum laminatum and the median plates of more sclerotized cuticle give the appearance of plaques or tubercles when the surrounding softer cuticle shrinks.

The largest number of specimens came from a study of the area in Glacier National Park burned by the disastrous 1988 Red Bench Fire, carried out 3 years after the fire ( White et al. 1994). Taracus specimens were found in both burned and unburned areas, in pine and in spruce forests, as well as from a meadow. We suspect that the Waterton Lakes National Park specimens were also collected as part of this same study, but one year later. The two parks are adjacent and generally referred to as Waterton Glacier International Peace Park.

Specimens vary considerably in size, males from about 3 mm long to over 5 mm; this largely depends on the size of the abdomen, but males from Montana and Alberta have distinctly smaller chelicerae and shorter legs and palpi than the few males from British Columbia, Oregon and Idaho. This may be due to many of the former specimens having been collected in recently burnt-over areas, expected to be poor in resources. Newly matured or teneral specimens may not have as well-sclerotized abdomens as older ones.

While T. pallipes occurs along the Pacific coast at low altitudes and is active during the winter months, the altitudes recorded for collections of T. gertschi are high for the latitude, and winter activity would seem to be precluded by low temperatures and snow cover. The Tekoa Mountain (Washington) records come from pitfall traps left out from October of one year to July of the next, so these specimens could have come from early and/or late in the period. Alternatively, the specimens may have been active in the subniveal space. All other dated collection records are from June to September. Accordingly, T. gertschi , like T. packardi , may be characterized as a highaltitude, summer-active species.

Figures

FIGURES 37 – 45. Taracus gertschi. Fig. 37, female palpus. Fig. 38, male palpus. Fig. 39, penis. Fig. 40, glans penis. Fig. 41, female, dorsal view. Fig. 42, female, lateral view. Fig. 43, female chelicerae, lateral view. Fig. 44, female chelicera, second article, frontal view. Fig. 45, male chelicera, lateral view.

Tables

TABLE 6. Lengths in mm of palpal and leg articles of male Taracus gertschi.

	Femur	Patella	Tibia	Metatarsus	Tarsus
Palpus	2.86	1.75	2.19	-	0.71
Leg 1	3.00	0.80	1.87	2.90	2.67
Leg 2	4.07	1.00	3.10	4.50	4.53
Leg 3	2.67	0.93	1.83	2.77	2.53
Leg 4	3.27	1.00	2.60	3.67	3.67

TABLE 7. Lengths in mm of palpal and leg articles of female Taracus gertschi.

	Femur	Patella	Tibia	Metatarsus	Tarsus
Palpus	3.46	2.06	2.65	-	0.87
Leg 1	3.17	1.00	2.06	3.00	2.40
Leg 2	4.33	1.16	3.34	4.53	4.83
Leg 3	3.09	1.00	2.12	3.00	2.20
Leg 4	3.83	1.16	3.10	4.33	3.83