Hylurgops pinifex ( Fitch, 1858 )

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 : 324-326

Hylurgops pinifex ( Fitch, 1858)

( Figures 3 b, 7d, 11a, 12b, 13a, 15d, 16b, 17d, 19)

Hylastes pinifex Fitch, 1858:729 (New York, USA) Hylurgops pinifex, LeConte, 1876:389

Hylastes glabratus, Heyden, 1890:132

Hylurgops glabratus, Riley, 1891:92

Hylastes (Hylurgops) decumanus, Hagedorn, 1910:46 H. (Hylurgops) pinifex, Hagedorn, 1910:46 H. rugipennis pinifex, Wood, 1982:90

Diagnosis. Hylurgops pinifex is reddish-brown dorsally and darker ventrally, but occurs as entirely red forms; the pronotum is broad and strongly constricted anteriorly ( Fig. 17 d). It is distinguished from H. rugipennis at> 50× magnification by the absence of a complete and distinct pronotal disc reticulation ( Fig. 16 b), by the more distinctly different-sized pronotal punctures ( Fig. 16 b), by the narrower 2nd declivital interstriae, by the thicker, whitish yellow declivital erect setae, by the absent or smaller granules and erect setae on the 2nd declivital interstriae (eastern form only), by the usually larger metatarsal socketed teeth, by the lack of the ventral lobe of the aedeagus ( Fig. 7 d), and for the most part by the distribution ( Fig. 19 ).

Description. Size. Length 4.1–5.3 (avg. 4.6 ± 0.3) mm long, 2.4× longer than wide. Color. Mature adult nearly black to reddish-brown with black spots on anterior margin of pronotum with ventral sclerites dark-reddish to black. Frons. Transverse impression moderate to subtle; carina sharply elevated, surface shiny or granulate; vestiture hair-like, longer below middle, 2–7× as long the diameter of a puncture. Pronotum. Broad, 0.9–1.0 (0.95 ± 0.03), slightly narrower than elytral base, distinctly constricted anteriorly ( Fig. 17 d), widest anterior to middle; lateral margin narrowly rounded on basal third, broadly rounded on middle third, constricted on anterior third; middle line slightly raised, extending from base up to entire pronotal length, its surface shiny (western) to subgranulate (eastern); discal punctures of three sizes, medium more abundant, larger 3× diameter of smaller, inner surface shiny to granulate, inter puncture spaces smooth to granulate, reticulation if present limited to basal and apical margins; vestiture sparse to absent on disc, short, recumbent, hair-like, pronotal vestiture absent or sparse, hair-like, recumbent, short (as long as small discal puncture’s diameter) on disc; approximately twice as long on margins Elytra. Anterior margin procurved ( Fig. 11 a), slightly raised dark margin; striae shallowly concave, averaging half as wide as interstriae on disc, punctures deep, coarse, keyhole-shaped ( Fig. 12 b), half their diameter apart on disc; interstriae smooth, glossy, with confused small punctures (seen at 100× or more) each with a short, recumbent, hair-like setae becoming scale-like on last third, uniseriate row of short, erect hair-like setae emerging from a central puncture, 1.5 discal striae diameter apart as long as diameter of a puncture on last third of disc. Declivity. Striae slightly impressed, a third width of interstriae, punctures elongate, deep, smaller than at disc separated by 0.75× their diameter; 2nd interstriae slightly impressed, 3rd widest, not intersecting 6th ( Fig. 13 a), with pointed granules, separated by 1.5–2× a puncture diameter, 2nd narrower, with reduced number of granules (eastern); ground vestiture consists of whitish-yellow abundant, recumbent scale-like setae and an uniseriate, erect hair-like setae as long as one striae. Ventral sclerites. Surface glossy, discretely reticulate; vestiture consists of short, recumbent hair. Legs. Tarsi dark reddish-brown; protibiae with two socketed teeth before apical angle; meso- and metatibiae with one or two large socketed teeth before apical angle. Variation. Western form differs from the eastern by the glossy pronotal surface, by the more regularly sized punctures, sometimes convergent, by the complete set of granules and setae on 2nd declivital interstriae, by the more distinctly setose elytral disc, by the darker coloration of specimens of Colorado and Wyoming. Aedeagus. Without a ventral lobe ( Fig. 7 d).

Male. Declivital hair-like setae longer.

Gallery: Egg gallery is longitudinal ( Fig. 3 b), slightly sinuate, and 50–85 mm long ( Blackman 1919), extending up or down from entrance hole, usually bellow the first meter bellow the duff layer of a dead tree or stump. The larvae burrow at both sides of the maternal gallery, their tunnels becoming confused at later stages of development.

Material examined. 458 specimens. CANADA. Alberta: Banff ( CNCI), Cypress Hills ( CNCI), Jasper Park ( CNCI), Laggan ( CNCI), Lake Louise ( CNCI), Olds ( CNCI), Waterton Lakes NP ( CNCI), Whirlpool River, Jasper ( CNCI). British Columbia. Aspen Groove ( CNCI), Glacier ( CNCI), Golden ( CNCI), Kleena kleene, “Tatler Lake” ( CNCI), Lorna ( CNCI), Marysville ( CNCI), McBride ( CNCI), Summit Lake, 392 mi. Alaska Hwy. ( CNCI), Trinity Valley ( CNCI). Manitoba: 30 mi. E Winnipeg ( CNCI), Gillam ( CNCI), Grass River Prov. Pk. ( CNCI), South of Clear lake, “RD” Riding Mountains ( CNCI). New Brunswick: Bathurst ( CNCI), Kouchibouguac NP ( CNCI), McGraw Brook ( CNCI), Plaster Rock ( CNCI), Saint Louis ( CNCI), Salmon River ( CNCI). Nova Scotia: Crescent Beach, Bridgewater ( CNCI), Halifax ( CNCI), Kejimkujik NP ( CNCI), Kentville ( CNCI). Ontario: Algonquin Pk. ( CNCI), Atikokan ( CNCI), Chalk River ( CNCI), Constance ( CNCI), Fort William ( CNCI), Frater ( CNCI), Ignace ( CNCI), “King Mtn.” Mont King, Gatinau Pk. ( CNCI), Kormak ( CNCI), Longlac ( CNCI), Marmora ( CNCI), Ottawa ( CNCI), Petawawa ( CNCI), Petawawa Res. ( CNCI), Prince Edward Co. ( CNCI), Quetico Park ( CNCI), Rainy River Dist. ( CNCI), Lake Huron, Seaforth ( CNCI), Sudbury ( CNCI), Thessalon ( CNCI), Toronto ( CNCI). Quebec: Fort Coulogne ( CNCI, DEBC), Hudson ( CNCI), Hull ( CNCI), Kazabazua ( CNCI), PSP Sta., Lake Opasatika ( CNCI), Laniel ( CNCI), Lennox and Addington ( CNCI), Lake Menphremagog ( CNCI), Montreal ( CNCI), “Sainte-Anne’s” de Beaupré ( CNCI), Queens Park, Aylmer ( CNCI). USA. Alaska: Ft. Yukon ( CNCI). California: Mariposa Co.: Tuolumne Meadows ( CNCI); Mono Co.: Blanco’s Corral, White Mts. ( CNCI); Tulare Co.: Near Mt. Brewer ( CNCI); Tuolumne Co.: Avalanche Meadows, Sequoia NP ( CNCI). Colorado: Boulder Co.: Longmont ( CSUC); Chaffe Co.: 17 km W Buena Vista, Cottonwood Pass Rd. ( DEBC); Grand Co.: Elk Creek, Fraser ( CNCI), Elk Creek, Fraser, Moffat Rd. ( CSUC), Tabernash ( CSUC), Williams Fork ( CSUC); Gunnison Co.: 10 mi. E Almont ( CSUC), Agate Cp. 6 mi. W Monarch Pass. ( DEBC); Jackson Co.: Cameron Pass ( CSUC); Jefferson Co.: ( CSUC); Larimer Co.: 9.1 km W Bellvue, Rist Canyon ( CSUC), Estes Park ( CSUC), Fort Collins ( CSUC); Teller Co.: Mueller State Park ( CSUC). Connecticut: Litchfield Co.: Cornwall ( CNCI). Idaho: Blaine Co.: Priest Rd. ( CNCI); Cassia Co.: Minidoka NF ( CSUC). Maine: Kennebec Co.: Monmouth ( CNCI); Somerset Co.: Norridgewock ( CNCI); Oxford Co.: Paris ( CNCI); Penobscot Co.: Orono ( UAIC, DEBC). Massachusetts: Middlesex Co.: Framingham ( CNCI). Minnesota: Cook Co.: Grand Portage Natl. Mnmnt. 0.8 km N Cowboys Rd./ Co. Rd 89 ( DEBC, CSUC); Itasca Co. ( DEBC); St. Louis Co.: Duluth ( CNCI). New Hampshire: Strafford Co.: Durham ( CNCI). New Jersey: (no county) DaCosta ( CNCI); New York: St. Lawrence Co.: Cranberry Lake ( DEBC); Tompkins Co.: Ithaca ( CNCI). North Carolina: Buncombe Co.: Ashville ( CSUC); Macon Co.: near Cliffside Lake Cpgd. NW Highlands ( CNCI). Oregon: (no county) Blue Mountains ( CNCI); (no county) Ochoco NF ( CNCI), Wallowa Co.: Minam NF ( CNCI), Whitman NF ( CNCI). Pennsylvania: Allegheny Co.: N Bloomfield ( CNCI); Hemmlock Island Co.: Cooksburg ( DEBC). Utah: Wasatch Co.: Lost Lake ( DEBC), Wolf Creek Pass. ( DEBC). Virginia: Montgomery Co.: Christiansburg ( CSUC). Wisconsin: Ashland Co.: Apostle Islands ( CSUC). Wyoming: Big Horn Co.: 34 mi. E Lovell, Porcupine Camp. ( CNCI); Riverton Co.: Dubois ( CSUC).

Hosts: Picea glauca , Pinus albicaulis , P. balfouriana , P. banksiana , P. contorta , P. resinosa , P. s t ro b u s, P. virginiana , Larix laricina , L. occidentalis .

Distribution ( Fig. 19 ). NORTH AMERICA, CANADA, and USA. Transcontinental from eastern

British Columbia to Nova Scotia, south to Central Colorado Rocky Mountains in the western populations. A record from western Arizona and one from north central New Mexico ( Snow 1881) may be accidental. The eastern population occurs from Canada to the extreme north of Georgia and South Carolina in the Appalachian Mountains. The map point on Mobile, Alabama does not represent a naturalized population ( Atkinson et al. 1991).

Discussion. Asa Fitch (1858) described Hylastes pinifex from specimens collected in New York. Later, LeConte (1868) supported the placement of H. pinifex in the genus Hylastes under Erichson’s (1836) second division. LeConte (1876) placed H. pinifex in his genus Hylurgops .

In the late 1800s Hamilton (1889, 1891), Heyden (1890), Hopkins (1893a, b), and Schwarz (1886) suggested that H. pinifex was the same species as the European H. glabratus , but that was not accepted by Blandford (1894, 1898). The Palearctic H. glabratus has more regularly sized pronotal punctures and shiny interspaces with some reticulation as does H. rugipennis , but it differs in that the first interstriae is wider than the second. Hylurgops glabratus differs from both H. pinifex and H. rugipennis in the complete lack of granules and the uniseriate row of hair-like setae on the second declivital interstriae. Hagedorn (1910) considered Hylurgops to be a subgenus of Hylastes , where he placed H. pinifex . Thereafter, the species has been placed in the genus Hylurgops .

Wood (1982) reduced H. pinifex to a subspecies of H. rugipennis based on the apparent hybridization of the two (see Discussion section of H. rugipennis for details). The characters used by Wood are variable and occur outside the “hybridization zone.” However, those of the narrower second declivital interstriae missing granules [eastern population], whitish-yellow vestiture, distinctly different-sized pronotal punctures [eastern population], and glossy to granulate surface of the pronotal interspaces [western population] are constant along the species’ distribution and are not observed in H. rugipennis .

Hylurgops pinifex is the only Nearctic species in this genus occurring in eastern North America (north of Mexico), where the main hosts are Pinus strobus and P. resinosa . The occurrence in both eastern and western North America (north of Mexico) may have been possible by using P. banksiana and Larix laricinia as a bridge across the North American boreal forest (see Fig. 19 ). The last two hosts extend to the Northern Rockies along Alberta’s and British Columbia’s southern border, where H. pinifex occurs in sympatry with H. rugipennis . The principal hosts in the west are P. contorta and P. ponderosa .

Hylurgops pinifex is considered a valid species supported by the consistent diagnostic features mentioned above in the species key and the diagnostic section. As several external morphological differences exist between the eastern and western forms of H. pinifex , a molecular approach may be useful to clarify the taxonomic status of these two forms.

Figures

FIGURE 3. Detail of Hylastini galleries: a) Pachysquamus subcostulatus, maternal (red) and larval gallery (adapted from Cibrián-Tovar et al. 1995), b) Hylurgops pinifex (eastern form), maternal (red) and larval gallery (adapted from Blackman 1919).

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 11. The anterior margin of elytra in the Hylastini. a) anteriorly procurved as in Scierus and some Hylurgops (H. pinifex), b) nearly straight as in most Hylastes (H. mexicanus).

FIGURE 12. Shape of elytral disc strial punctures in Hylurgops: a) round (H. longipennis), b) keyhole-shaped (H. pinifex), and c) keyhole-shape variation (H. planirostris).

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.