Scolytus rugulosus ( Mueller , 1818)

Smith, Sarah M. & Cognato, Anthony I., 2014, A taxonomic monograph of Nearctic Scolytus Geoffroy (Coleoptera, Curculionidae, Scolytinae), ZooKeys 450, pp. 1-182 : 23-24

Taxon classification Animalia Coleoptera Curculionidae

Scolytus rugulosus ( Mueller, 1818) Fig. 14

Bostrichus rugulosus Müller, 1818: 247.

Scolytus rugulosus ( Müller, 1818): Eichhoff 1881: 41.

Scolytus rugulosus For complete taxonomic history see Wood and Bright (1992).

Diagnosis.

Both sexes of Scolytus rugulosus are distinguished by the rounded elytral apices, by the serrate and deeply emarginated elytral apex, and by the oblique ventrite 2.

Description (male).

1.9-2.6 mm long (mean = 2.4 mm; n = 10); 2.1-2.7 times as long as wide. Color red-brown to dark red brown, antenna yellow-brown. Pronotum typically darker than elytra.

Head. Epistoma weakly, broadly emarginate; epistomal process absent; median area above mandibles bearing dense patch of long, yellow, hair-like setae. Frons appearing convex when viewed laterally, slightly transversely impressed just above epistoma; moderately, finely, longitudinally aciculate-punctate; aciculations converging at epistoma; punctures small, coarse; moderately, uniformly covered by long, fine, yellow erect hair-like setae, these longer than width of midpoint of eye. Antennal scape short, elongate; club flattened, irregularly ovoid, setose with partial septum, two arcuate sutures visible.

Pronotum wider than long; apical margin broadly rounded, median area between eyes lined with scales; sides distinctly arcuate, strongly constricted near apex, forming a weak transverse impression near apical margin; surface smooth, shining, punctures on disc fine, shallow, moderately abundant, larger and more abundant laterally and on apical constriction; apical and anterolateral margins bearing sparse, erect, yellow setae; base weakly bisinuate.

Elytra with sides sub-parallel on basal half, narrowing to strongly rounded, moderately serrate apex; apex strongly emarginated at suture. Margin of apical edge bearing large, coarse punctures. Disc glabrous, smooth, shining; interstriae not impressed and equal in width to striae, interstrial punctures uniseriate, equal in size to those of striae, bearing moderately abundant short, semi-erect yellow-brown hair-like setae; striae not impressed. Declivity bearing sparse, short, erect yellow setae. Metepimeron less than half-length of metanepisternum.

Venter. Apical margin of ventrite 1 rounded, flush with base of ventrite 2. Ventrite 2 nearly at an oblique angle to ventrite 1; surface shagreened, dull finely punctate; punctures small, coarse, shallow; surface flattened, unarmed; setae abundant, erect, long, greater than length of segment 3; lateral margins of ventrites 2-3 and ventrite 4 unarmed. Ventrite 5 carinate ridge closer to apical margin of segment; length of ventrite 5 greater than combined lengths of ventrites 3 and 4; setal patch absent, median depression present.

Female.

2.0-3.1 mm long (mean = 2.5 mm; n = 10); 2.1-2.8 times as long as wide. Similar to male except frontal setae sparser, shorter, less than width of eye.

Specimens examined.

102.

Type material.

Syntypes: (ISNB, ZIFH). None examined.

Non-type material.

CANADA:BRITISH COLUMBIA: Vancouver, 5.VII.1975, N.M. Downie (FMNH-2). NOVA SCOTIA: Middleton, 11.VI.1938 (CNCI-2). ONTARIO: Brimley, 17.VII.[19]21 (CNCI-1), 30.VII.[19]22 (CNCI-1). Ottawa, 21.VIII.1999, A.T. Howden, ex. wild grape [= Vitis sp.] (CNCI-1). Simcoe, 3.IX.1931, J.A. Hall (CNCI-2). Smith Falls, V.1940, H.S. Fleming (CNCI-1). UNITED STATES:ARIZONA: [Cochise Co.]: Green Canyon, 26.IX.[19]98, Sequeira and Jordal, ex. Fraxinus sp. (ZMBN-1). CALIFORNIA: [Los Angeles Co.]: San Marino, 25.VI.[19]42, G.P. Mackenzie (FMNH-1). [Orange Co.]: Santa Ana, 1.IV.1943, L.R. Gillogly, ex. bait traps (USNM-1). [Placer Co.]: Penryn, 1.X.1929, A.T. McClay (FMNH-2). DELAWARE: [Kent Co.]: Camdem, XII.1940, J.M. Amos (FMNH-1). INDIANA:Madison Co.: 10.VIII.1937, ex. apricot [= Prunus armeniaca ] (FMNH-2). Porter Co.: Jackson Township, Maple Knoll Farm, 6.IV.[19]60, C.C. Gregg (FMNH-10). Tippecanoe Co.: 7.VI.1956, N.M. Downie (FMNH-2), 1.XI.1978 (FMNH-1). MICHIGAN:Allegan Co.: Fennville area, 30.VI.2003, P. McGhee, ex. on apple trees [= Malus sp.] (MSUC-1). [Cass Co.]: Edwardsburg, 30.VIII.1928 (MSUC-6). [Ingham Co.]: [East Lansing], Agriculture College [= Michigan State University campus], 1.I.1917 (MSUC-3). Isabella Co.: 16.IX.[19]55, R.R. Dreisbach (MSUC-1). [Kent Co.]: Grand Rapids, 17.X.[19]11 (MSUC-6). [Lenawee Co.]: Adrian, 20.VII.1900 (MSUC-7). Livingston Co.: Howell, 214 Inverness St, N42.61678°, W84.92810°, 23.V-7.VI.2007, R. Mech, ex. Lindgren trap with EtOH + alpha (MSUC-1). Midland Co.: 24.VII.[19]46, R.R. Dreisbach (MSUC-1), 14.IX.[19]56 (MSUC-1). Oakland Co.: A.W. Andrews (MSUC-1); 28.VI.[19]47, B. Summerville (MSUC-1). [Washtenaw Co.]: Manchester, 21.V.1913 (MSUC-4), 31.V.1913 (MSUC-7). NEW YORK:Onondaga Co.: Syracuse, X.1987, R.J. Rabaglia, ex. mountain ash [= Sorbus sp.] (RJRC-1). [Tompkins Co.]: Ithaca, ex. peach [= Prunus sp.] (CASC-1). [Ulster Co.]: Oliverea, 20.VI.[19]18 (USNM-1). Wayne Co.: 26.VI.1950, Shumaker (USNM-1), 8.VIII.[19]51 (USNM-1). [Unspecified County]: (CASC-2). PENNSYLVANIA:Allegheny Co.: Upper St. Clair Township, 28.VIII.[19]59 (EMEC-1). [Philadelphia Co.]: Philadelphia, 20.V.[18]98 (USNM-1). UTAH: [Utah Co.]: Vineyard, 6.IX.[19]23, T. Spalding (USNM-1). WASHINGTON: [Whitman Co.]: Steptoe Butte State Park, 9.VII.1971, N.M. Downie (FMNH-1). WASHINGTON, D.C.: 26.VII.1943, L.J. Bottimer, ex. on Prunus sp. (CNCI-2). ADDITIONAL SPECIMENS:Brazil (MSUC-21), Czech Republic (MSUC-1), Hungary (MSUC-1), Morocco (MSUC-1) and Italy (MSUC-2).

Distribution.

CANADA: British Columbia, New Brunswick, Nova Scotia, Ontario, Prince Edward Island. Greenland. MEXICO: Durango. UNITED STATES: Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Utah, Virginia, Washington, Washington D.C, West Virginia, Wisconsin (Fig. 15).

Hosts.

Stone and pome fruit trees including Malus spp. (apple), Pyrus spp. (pear), and Prunus spp. (cherry) and is less common in Crataegus (hawthorn), Sorbus (mountain ash) and Ulmus spp. (elm).

Common name.

Shothole borer.

Biology.

Scolytus rugulosus primarily attacks and kills small twigs and branches but may kill whole trees through the process of excavating adult galleries and larval feeding. Twig injury is the result of feeding activity at the base of the bud. Attacks can begin near an injury or on a healthy tree ( Chamberlin 1939; Bright and Stark 1973).

The adult gallery is parallel to the grain of the wood and solely consists of an egg gallery; a nuptial chamber is not constructed. The adult gallery strongly scores the cambium, lightly scores the sapwood and ranges in size from 1.0-5.0 cm in length (Bright and Stark 1976; Furniss and Johnson 2002). Eggs are laid singly in larval niches on both sides of the egg gallery. Larval mines first radiate perpendicular to the egg gallery against the grain of the wood and later turn parallel to the grain ( Bright and Stark 1973). The larval stage typically lasts one month. Pupation occurs in the bark for summer emergence. If the brood is unable to complete development during the warmer months, larvae will burrow 1.0-2.0 cm deep within the sapwood to overwinter. The following year, adults emerge and feed at twig crotches before selecting host material ( Baker 1972). There are one to four generations per year depending on locality, with more generations occurring in warmer climates ( Chittenden 1898; Baker 1972; Wood 1982).

Remarks.

This species is native to the Palearctic region and was first detected in North America in 1877 from New York ( Chittenden 1898). The native range of Scolytus rugulosus encompasses Europe, North Africa, Asia Minor and middle Asia to Zabaikalye (Russia) ( Michalski 1973; Knížek 2011).