Scolytus dentatus Bright, 1964

Smith, Sarah M. & Cognato, Anthony I., 2014, A taxonomic monograph of Nearctic Scolytus Geoffroy (Coleoptera, Curculionidae, Scolytinae), ZooKeys 450, pp. 1-182 : 31-32

Taxon classification Animalia Coleoptera Curculionidae

Scolytus dentatus Bright, 1964 Figs 28-29

Scolytus dentatus Bright, 1964: 167.

Diagnosis.

The Scolytus dentatus male is easily distinguished by the endemic distribution in the Santa Lucia range of California, and by the presence of a median denticle on the apical margin of ventrite 4, occasionally median denticles may also be present on the apical margins of ventrites 2 and 3. The female is distinguished by its distribution and differentiated from the Scolytus praeceps female by the presence of a strongly developed and distinct epistomal process and larger size.

Description (male).

3.0-4.0 mm long (mean = 3.45 mm; n = 15); 1.7-2.5 times as long as wide. Head, pronotum and abdominal venter dark red-brown, antennae light brown, legs dark red-brown to light brown, elytra light red-brown. Pronotum darker than elytra.

Head. Epistoma moderately, acutely emarginated; epistomal process strongly produced, elevated; median area above mandibles bearing dense patch of long, yellow, hair-like setae. Frons appearing flattened when viewed laterally, not impressed; moderately, finely, longitudinally aciculate, coarsely 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, 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, punctulate, punctures moderately abundant, larger and more abundant laterally and on apical constriction; apical and anterolateral margins bearing sparse, erect, yellow, hair-like setae; base weakly bisinuate.

Elytra with sides sub-parallel on basal half, narrowing to subquadrate, smooth apex; apex entire at suture. Margin of apical edge bearing large, coarse punctures. Disc glabrous, smooth, shining; interstriae not impressed, more than twice width of striae, punctures uniseriate, smaller than those of striae; striae weakly impressed. Declivity bearing sparse, short, erect yellow setae. Metepimeron half-length of metanepisternum.

Venter. Apical margin of ventrite 1 strongly produced, elevated above base of ventrite 2, ventrite base 2 appearing impressed. Ventrite 2 nearly perpendicular to ventrite 1; surface glabrous, shagreened, dull, finely, obscurely punctate; punctures small, fine and shallow; surface flattened. Apical margins of ventrites 2 and 3 may be armed with median denticle, median denticle always present on apical margin of ventrite 4; lateral margins of ventrites 2-4 unarmed. Ventrite 5 carinate ridge closer to apical margin of segment; length of ventrite 5 equal to combined lengths of ventrites 3 and 4; setal patch and median depression absent.

Female.

3.4-4.6 mm long (mean = 3.7 mm; n = 15); 2.2-2.5 times as long as wide. Similar to male except epistoma less strongly emarginated, epistomal process less strongly produced and elevated, frons convex when viewed laterally, weakly longitudinally aciculate, setae sparser, shorter, less than width of eye; weakly medially impressed between inner apices of eyes. Ventrites unarmed.

Specimens examined.

95.

Type material.

Holotype Scolytus dentatus Bright: male, labeled "Calif: Monterey Co, Cone Peak, 6-29-[19]63, Abies bracteata , C.J. Wray Collector" (CASC). Allotype, female, Scolytus dentatus , identical data as holotype. Paratypes: UNITED STATES:California:Monterey Co.: Cone Peak, 29.VI.[19]63, C.J. Wray, ex. Abies bracteata (CASC-6, CNCI-20, EMEC-39, USNM-8). Carmel Valley, 15 mi S., 22.VII.[19]63, C.J. Wray, ex. Abies bracteata , (CASC-4).

Non-type material.

UNITED STATES:California:Monterey Co.: Carmel Valley, 15 mi S., 23.VII.[19]63, D.E. Bright, ex. Abies bracteata (CASC-2); 30.VII.1964 (CASC-2). Cone Peak, 29.VI.[19]63, C.J. Wray, ex. Abies bracteata (CASC-1, USNM-12). Williams Canyon, Los Padres National Forest, 24.IV.1992, D.E. Bright, G. Ferrell, ex. Abies bracteata limbs (CNCI-1).

Distribution.

UNITED STATES: California (Fig. 30).

Hosts.

Abies bracteata (D. Don) Poit. (bristlecone fir / Santa Lucia fir).

Biology.

Little is known regarding the biology of this uncommon and narrowly geographically restricted species. The host, Abies bracteata , is restricted to the Santa Lucia Mountains of California. The tree is distributed in small patches in deep, moist canyon bottoms as well as dry, rocky slopes and ledges within Los Padres National Forest in Monterey County, especially near Cone Peak and Church Creek ( Griffin and Critchfield 1972; Sullivan 1993). Scolytus dentatus has been collected feeding in the bole of large standing trees ( Bright 1964) but is also reported from larger limbs and fresh slash ( Edson 1967).

The adult gallery somewhat resembles an expanded ‘E’ (Fig. 24). The gallery is parallel to the grain of the wood and consists of a central nuptial chamber and two egg galleries, one below and one above the nuptial chamber. Each egg gallery ends in a pronounced hook. Galleries strongly score the cambium and lightly score the sapwood. The adult gallery averages 2.5-12.0 cm in length ( Bright 1964; Edson 1967). Egg niches are closely spaced on both sides of the maternal gallery ( Bright and Stark 1973). Larval mines are first perpendicular to the egg gallery and later turn to form a fan shaped pattern before terminating at pupation chambers in the sapwood ( Edson 1967).

Remarks.

Considerable variation is observed in the presence of median denticles on the apical margins of male ventrites 2 and 3. Frequently males only have a median denticle on the apical margin of ventrite 4 as those on 2 and 3 may or may not be present in the male. This species is related to Scolytus robustus and Scolytus subscaber based on morphological characters (Fig. 2). Both of these species also feed on true firs ( Abies spp.) and have the apical margin of male ventrite 1 strongly apically produced.