Hylurgops rugipennis ( Mannerheim, 1843 )

Mercado-Vélez, Javier E. & Negrón, José F., 2014, Revision of the new world species of Hylurgops LeConte, 1876 with the description of a new genus in the Hylastini (Coleoptera: Scolytinae) and comments on some Palearctic species, Zootaxa 3785 (3), pp. 301-342 : 321-323

Hylurgops rugipennis ( Mannerheim, 1843)

( Figures 5 a, 6d, 7c, 13b, 15c, 16a, 17c, 19)

Hylurgus rugipennis Mannerheim, 1843:297 (Sitka Island, Alaska, USA, lost) Hylastes rugipennis, Mannerheim, 1852:385 (not previously documented) Hylurgops rugipennis, LeConte, 1876:390

H. rugipennis rugipennis, Wood, 1982:89

H. rugipennis pinifex, Wood, 1982:90

Diagnosis. Hylurgops rugipennis is reddish brown above, usually darker ventrally and its pronotum is broad and strongly constricted anteriorly ( Fig. 17 c). It is distinguished from H. pinifex at> 50× magnification by the distinct and complete pronotal reticulation ( Fig. 16 a), by the regularly-sized pronotal punctures ( Fig. 16 a), by the narrower metatibia, by the ventral lobe of the aedeagus ( Fig. 7 c), and by its more restricted distribution ( Fig. 19 ).

Description. Size. Length 3.7–4.7 (avg. 4.2 ± 0.3) mm long, 2.4× longer than wide. Color. Mature adult reddish to brownish-red with dark spots on anterior margin of pronotum, ventrally dark reddish-brown to nearly black, ventrites light reddish-brown. Frons. Transverse impression strong ( Fig. 5 a); inter-puncture areas reticulate, rarely shiny; carina broadly elevated, surface shiny; vestiture hair-like, longer on lower half, 2–7× the length of a puncture’s diameter. Pronotum. Broad, 0.9–1.0 (0.93 ± 0.02), slightly narrower than elytral base, distinctly constricted on anterior third, widest anterior to middle; lateral margin narrowly rounded on basal fourth, becoming broadly rounded on central two fourths and broadly constricted on anterior fourth; middle line slightly raised, extends from base sometimes across entire pronotal length, discal surface reticulate ( Fig. 16 a), rarely glossy; discal punctures of two equally abundant sizes, small two-thirds the size of large, inner surface shiny, inter puncture area reticulate; vestiture short, recumbent, hair-like setae indistinct to the length of a large discal punctures on disc, 2× the length near margins. Elytra. Anterior margin moderately procurved, slightly raised dark margin; striae shallowly concave with round to keyhole-shaped, smooth, dark punctures, averaging half their diameter apart at disc; interstriae wide as first striae, wider than rest, smooth, shiny, minutely punctate (seen at> 50× magnification), each with a short, recumbent hair-like setae becoming scale-like on posterior half to declivity and a central punctate granule with a long, sub-erect hair-like setae as long as a strial puncture appearing as rugosities on disc, separated by length of 1.5 strial puncture diameter. Declivity. Striae slightly impressed, less than half as wide as interstriae, punctures oval and deep, some keyhole-shaped, smaller than at disc, separated by distance equal to their diameter, 2nd interstriae slightly impressed, wider than 1st, 3rd widest to equal than 2nd, usually intersecting 6th ( Fig. 13 b) all with regularly spaced pointed granules, 2 punctures width apart; vestiture scale-like, short, recumbent, confused and a central reddish, erect, hair-like setae as long as strial width. Ventral sclerites. Surface punctured, interspaces reticulate; recumbent setae hair-like, as long as size of three punctures or more; precoxal ridge acutely elevated. Legs. Tibia reddish, narrower than in other species; protibiae with 1 or 2 mid-sized socketed teeth before apical angle, mesotibiae with 2 mid-sized socketed teeth before apical angle, and metatibiae broad with 3 medium-sized socketed teeth before apical angle; third tarsal segments bilobed, broader than second. Aedeagus. Showing a distinct ventral lobe ( Fig. 7 d).

Male. Declivital hair-like setae longer.

Gallery: Maternal gallery longitudinal, slightly sinuate, extending up and down from entrance hole ( Bright & Stark 1973), usually just over the root collar of a dead tree or stump. Larval galleries extend perpendicular to brood gallery becoming confused at later stages. These galleries can extend into the roots, often at considerable distance from the brood gallery ( Bright & Stark 1973).

Material examined. 250 specimens. CANADA. Alberta: Red Rock Cny. Waterton Lakes NP ( CNCI). British Columbia: Creston ( CNCI), 8 mi. W Creston ( CNCI), 21 mi. W Creston ( CNCI), 2 mi. S Salmo River, Creston ( CNCI), Glacier ( CNCI), Inverness ( CNCI), 12 mi. S Long Beach, Tofino ( CNCI), Lorna ( CNCI), Mainland ( CNCI), Massett, Graham Is. QCI ( CNCI), 4.7 km N Renell Sound Rd. Ghost Cr., Graham Is. ( CNCI), Sicamous ( CNCI), Skidegate, Graham Is. ( CNCI), Stanley Park, Vancouver ( CNCI), 1 mi. NW Tlell, Graham Is., QCI ( CNCI), Tow Hill, Graham Is. ( CNCI), Trinity Valley ( CNCI, DEBC), Vancouver ( CNCI), Laskeek Bay, Reef Island, QCI ( CNCI). USA. Alaska: 15 km N Juneau, Chichagof Is. ( DEBC), Douglas Is. ( DEBC), N end Douglas Is ( CNCI); 12 mi. N Juneau ( DEBC), 41.5 km N Juneau ( CNCI); Juneau ( DEBC). California: Del Norte Co. ( CNCI); El Dorado Co.: Blodgett Forest UC, 10 mi. E Georgetown ( CNCI); Fresno Co. ( CNCI); Humboldt Co.: Eureka ( CNCI); Marin Co.: 1 mi. SE Inverness ( CNCI); Mendocino Co.: Mendocino ( DEBC); Monterey Co.: Carmel ( CNCI), Monterey ( CNCI); San Mateo Co.: Año Nuevo, 28 km NNE of Santa Cruz ( CNCI); Santa Cruz Co.: Swanton ( CNCI); Sonoma Co.: Salt Point St. Park ( DEBC); Tulare Co.: Kaweah R., Mid Fork ( CNCI). Idaho: Kootenai Co.: Coeur d'Alene NF ( CSUC). Oregon: Clatsop Co.: app. 3 mi. SE of Olney ( CNCI); Lincoln Co.: Otis, Cascade Head Exp. For. ( CNCI); Linn Co.: Santiam Pass ( CNCI, DEBC); Tillamook Co.: Kiwanda viewpoint on Cape Lookout, 2.5 mi. N 1.5 mi. W Sand Lake ( CNCI); Wasco Co.: Wapinitia ( DEBC). Washington: (no county) Mount Rainier NP ( CNCI, CSUC), (no county) Nisqually R. Mt. Rainier NP ( CNCI); Grays Harbor Co.: Westport ( CSUC); Jefferson Co.: Hoh Ranger Station, Olympic NP ( CNCI); Pierce Co.: West Side Mt Rainier ( CSUC); West Side Rd. 1.6N Hwy 706 ( CSUC).

Hosts: Abies concolor , A. lasciocarpa , Callitropsis nootkatensis (see Patterson & Hatch 1945), Larix occidentalis , Picea engelmannii , P. sitchensis , Pinus attenuata , P. balfouriana , P. banksiana , P. contorta , P. lambertiana , P. monticola , P. muricata , P. ponderosa , P. radiata , Pseudotsuga menziesii , Tsuga heterophylla .

Distribution ( Fig. 19 ). NORTH AMERICA. CANADA and USA. Kodiak Island, Alaska to Monterey and Tulare in southern California; mostly east of the Rocky Mountains.

Discussion. Mannerheim (1843) described Hylurgus rugipennis from the Sitka Peninsula in Alaska, and placed it in the genus Hylastes in 1852. LeConte (1868) and Chapuis (1869, 1873) supported the placement under Erichson’s (1836) second division of the genus Hylastes . LeConte (1876) placed H. rugipennis in his genus Hylurgops .

Wood (1971a) considered that H. rugipennis hybridized with H. pinifex in an area east of the Canadian Cascades to Vernon in British Columbia, later Bright (1976) considered this hybridization area to extend into Alberta. Wood (1982) reduced H. rugipennis to a subspecies because of the apparent intergrades in the above area, but the characters used to define the intergrades were not detailed by Wood (1971a, 1982). Bright (pers. comm.) mentioned that the character used by Wood to determine the hybrids of the two species was the distribution of the scale-like setae cover in the elytra. This suggests that in the “intergradation zone,” H. rugipennis has scale-like setae extending anteriorly into the elytral disc as in H. pinifex , in contrast to the coastal forms of the species in which the scales are limited to the declivity.

While considering it a subspecies, Wood (1982) described the phenotypes of H. r. rugipennis occurring throughout the Pacific Northwest as morphologically and biologically distinct from H. r. pinifex . Also, the distribution of the scale-like setae used in his subspecies determination represents a variation occurring across the two species’ distributions that was not observed by Wood (1982). Other characters such as the reticulate surface of the pronotal interspaces and the more regularly sized pronotal punctures of H. rugipennis are constant throughout the two species’ distributions. The fact that H. rugipennis was found in areas where its host Pinus monticola and some of the known hosts of H. pinifex co-occur, but apparently not in areas where these conditions are not met explains the species’ sympatry in areas in Alberta, British Columbia and the Sierra Nevada of California (see black arrows, Fig. 19 ). In this revision, H. rugipennis is treated as a distinct species from H. pinifex based on the characters specified in the key and other characters included in the description of the two species.

Hylurgops rugipennis , as defined herein, is restricted to the coastal forests of the Pacific Northwest from Kodiak Island in Alaska to Monterey in California and east to the Northern Rockies in Alberta, British Columbia; Idaho; Washington; and the Sierra Nevada of California ( Fig. 19 ). In its coastal range from Alaska to extreme northern California, the species occurs primarily in Picea sitchensis . South from there, the species’ range seems determined by the occurrence of the coastal “closed cone pine” species, Pinus attenuata , P. muricata , and P. radiata . The distribution of H. rugipennis east of the Canadian Cascade Mountains into the Northern Rockies primarily follows the distribution of P. monticola , which extends up to the Waterton Lakes National Park in Alberta. In the Sierra Nevada, the southernmost distribution of the species into central California appears delimited by this conifer host as well.

Figures

FIGURE 5. Depth of the mid-frontal impression of Hylurgops and Hylastes: a) deep and distinct (Hylurgops rugipennis), b) indistinct or absent (Hylastes mexicanus).

FIGURE 7. Aedeagus of the New World Hylurgops and Pachysquamus: a) Pachysquamus subcostulatus, b) Hylurgops planirostris, c) H. rugipennis, d) H. pinifex, e) H. incomptus, f) H. longipennis, g) H. knausi, h) H. reticulatus, and i) H. porosus.

FIGURE 13. Declivity strial pattern of Hylurgops: a) third striae not touching the sixth (H. pinifex eastern form), b) third striae sometimes touching the sixth (H. rugipennis).

FIGURE 16. Prothoracic discal surfaces of Hylurgops rugipennis and the eastern form of H. pinifex: a) reticulate and dull, sometimes shiny with similarly-sized punctures (H. rugipennis), b) shiny (eastern form), subgranulate (western form) with distinct, differently-sized punctures (H. pinifex).

FIGURE 17. Prothoraces of the New World Hylurgops: a) H. palliatus, b) H. planirostris, c) H. rugipennis, d) H. pinifex, e) H. incomptus, f) H. longipennis, g) H. knausi, h) H. reticulatus, and i) H. porosus.

FIGURE 19. Species distribution with main hosts: Hylurgops rugipennis (orange) and H. pinifex (black-gray). Arrows indicate sympatric areas where the two species and their respective main hosts co-occur.