Agrilus betulanigrae, Macrae, Ted C., 2003

Macrae, Ted C., 2003, Agrilus (s. str.) betulanigrae MacRae (Coleoptera: Buprestidae: Agrilini), a new species from North America, with comments on subgeneric placement and a key to the otiosus species-group in North America., Zootaxa 380, pp. 1-9 : 2-6

Agrilus (s. str.) betulanigrae n. sp.

Holotype (male)

“ USA: MO [Missouri]: Carter Co. Ozark National Scenic Riverway, Big Spring cpgd, T27N R1E S31 (SE¼), TCMacRae [p] / [field journal #] 01­24e: em. 1­7.V.2001 ex. [2–4 cm dia.] fallen dead branch Betula nigra coll. 14.IV.2001 [p] / HOLOTYPE Agrilus betulanigrae [p] ♂ [h] MacRae [p] [red label]”.

The holotype will be deposited in the United States National Museum, Washington, DC.

Diagnosis

Narrowly elongate, subcylindrical ( Fig. 1 ); upper surface moderately shining, head bright metallic blue, aeneous on vertex, pronotum aeneous on disc, blue on sides, elytra black with aeneous reflections, faint cupreous reflections on apices, ventral surface dark aeneous blue, more strongly shining than above; faintly setose. Males of A. betulanigrae are distinguished by their bent, subquadrately expanded genitalia ( Figs. 2–3 ). Females can only be identified in association with males.

Description

Measurements: length: 3.75 mm; width: 0.90 mm.

Head: frontovertex shallowly convex with faint median longitudinal sulcus extending from epistoma to vertex, lower part of sulcus broader; surface finely granulose, rather coarsely punctate dorsally, punctures forming vague concentric circles on each side of midline, more sparsely and evenly distributed on front, moderately clothed on ventral half and along ocular margins with long, silvery white pubescence; epistoma strongly transverse, anterior margin broadly but not deeply, arcuately emarginate; eyes large, strongly oblong, slightly more broadly rounded dorsally than ventrally, inner margins straight.

Antennae: extending nearly to posterior margin of pronotum when laid alongside, inconspicuously setose; antennomere 2 fusiform; 3 narrower and subequal in length to 2; 4­10 serrate, slightly longer than wide except 10 which is as long as wide; 11 oblong.

Pronotum: 1.25 times wider than long, posterior margin slightly narrower than anterior margin of elytra, widest along apical half, sides diverging from posterior margin to near middle, then subparallel; posterolateral angles quadrate; in lateral view marginal and submarginal carinae feebly sinuate, narrowly separated anteriorly, becoming contiguous just before posterior angle; anterior margin sinuate, broadly, arcuately produced medially; posterior margin transversely bisinuate, arcuately emarginate anterior to scutellum; disc moderately convex, with two round, feeble, longitudinally arranged median depressions and rather broad, oblique depressions along lateral margins; prehumeral carinae short, feeble, nearly obsolete; surface coarsely, transversely rugose, less distinctly so anteriorly and laterally, with numerous fine punctures between the rugae.

Scutellum: narrowly quadrate in front, triangular behind, strongly transversely carinate, about as long as wide, surface reticulate.

Elytra: subequal in width at base and beyond middle, lateral margins shallowly emarginate in between, apices narrowly, separately rounded, finely serrate; disc somewhat flattened, each elytron with a broad, moderately deep basal depression and an indistinct longitudinal costa, sutural margin recessed behind scutellum and strongly elevated posteriorly; surface densely imbricate­punctate, more shallowly, irregularly so near apices; minutely, sparsely setose.

Ventral surface: prosternum sparsely clothed with inconspicuous appressed setae, prosternal process slightly converging between coxae, acute at apex, prosternal lobe declivous, subtruncate, feebly emarginate at middle, surface reticulate, finely punctate; posterior coxae densely, coarsely punctate, moderately setose, posterior margin broadly, arcuately emarginate, upper angle perpendicular; abdominal ventrites finely, rather densely punctate, becoming faintly rugose on basal ventrites, sparsely clothed with fine, recumbent setae that become longer apically, ventrites 1 and 2 feebly flattened medially, suture between nearly obsolete; last ventrite sparsely, coarsely punctate, broadly rounded at apex.

Legs: femora subfusiform; tibiae straight, slender, armed with a small tooth on inner apical margin; metatarsus about as long as metatibia, metatarsomere 1 equal in length to remainder of metatarsus; tarsal claws similar on all legs, cleft near middle, outer tooth acute at apex, inner tooth broader and turned inward, nearly contiguous with opposite tooth.

Male genitalia ( Figs. 2–3 ): in lateral view bent sharply downward in basal half; parameres subquadrately expanded in apical half, angled obliquely downward laterad, narrowed suddenly before apex, apices transluscent, bearing long, curved, silky setae; tip of median lobe subacute.

Female

Differs from male in being more robust, front of head broader, more convex, cupreous with aeneous tinge on upper frons and vertex, more sparsely clothed with long white pubescence on lower half and along ocular margins; outer antennomeres slightly wider than long; pronotum aeneous with faint cupreous reflections, especially laterally; elytra aeneous black; beneath black with faint cupreous reflections; abdominal ventrites 1 and 2 convex medially; tibiae unarmed on inner apical margin; metatarsus shorter than metatibia.

Va r i a t i o n

Coloration was rather constant in the four males examined, while in females some variation was noted in the intensity of the cupreous and aeneous reflections on the head and pronotum. The prehumeral carinae vary from weak but distinct to nearly obsolete, and the pronotal depressions are more scarcely indicated in some specimens. The prosternal lobe is usually feebly emarginate medially but is a little more distinctly so in some specimens. Males measured 3.75–4.85 0.90–1.15 mm (mean = 4.35 1.02 mm, n = 4) and females 4.40–4.95 1.05–1.20 mm (mean = 4.70 1.13 mm, n = 8).

Material examined

In addition to the holotype, 3 male and 8 female paratypes: same data as holotype (3 ♂♂, 3 ♀♀); same data as holotype except em. 8–15.V.2001 (1 ♀); same locality, em. 1– 7.VI.2002 (2 ♀♀), 8–15.VI.2002 (1 ♀), and 23–30.VI.2002 (1 ♀) ex 2–4 cm dia. fallen dead branch B. nigra coll. 6.IV.2002, T. C. MacRae. Paratypes deposited in the following collections: GHNC, HAHC, TCMC, USNM. In addition to the type series, three females were examined from two additional localities in the state: MISSOURI: Butler Co., Big Cane Conservation Area, 3.5 mi S of Neelyville, T22N R5E S35: em. 23–30.IV.2001 ex 1– 3 cm dia. fallen branches B. nigra coll. 8.IV.2001 (2 ♀♀), T. C. MacRae; Clark Co., vic. SW corner Rose Pond Conservation Area, T64N R6W S23 (SC1/9), em. 24­31.V.2002 ex fallen branch B. nigra coll. 7.IV.2002 (1 ♀), T. C. MacRae (all deposited TCMC). These females almost certainly represent A. betulanigrae based on larval host but were not designated paratypes since no male specimens were associated with them.

Type locality

The type locality is a National Park Service campground in a mesic bottomland forest along one of the larger, spring­fed, gravel­bottomed rivers dissecting the Ozark Plateau in southeastern Missouri. Dominant woody plant species in this natural community include Acer saccharum L., Carya cordiformis (Wangenh.) K. Koch , Celtis occidentalis L., and Quercus alba L., with Diospyros virginiana L. and Juglans nigra L. also being characteristic (Nelson 1985).

Hosts

The type series was reared from small, fallen dead branches of river birch, Betula nigra L. This plant is widely distributed across the eastern United States and is the only species of Betula found in the middle and southern latitudes of the country. In Missouri, it grows naturally throughout the state in alluvial ground along streams and borders of gravel bars (Steyermark 1963) and is a dominant species in the wet bottomland forests of the southeastern lowlands (Nelson 1985). The trees with which the type series was associated may have been planted. Other Agrilus spp. that have been associated with Betula in North America include A. acutipennis Mannerheim, A. anxius Gory, A. cyanescens (Ratzeburg) , A. obsoletoguttatus Gory, A. olivaceoniger Fisher, and A. pensus Horn (Knull 1922, Fisher 1928, Bright 1987). Of these, only A. pensus has been reared from B. nigra (Fisher 1928, Knull 1930, MacRae and Nelson 2003). No other member of the otiosus species­group has previously been associated with Betula .

Comparisons

Males of A. betulanigrae will key to A. frosti Knull (Fisher 1928, Wellso et al. 1976, MacRae 1991); however, they can be immediately distinguished from this and all other congeners by their distinctively bent genitalia with subquadrately expanded parameres that are suddenly narrowed apically. Gayle Nelson kindly compared a male paratype with the unique holotype of A. hazardi Knull and confirmed they are not the same species. Females lack distinguishing morphological characters that allow them to be separated from females of related species.

Etymology

The specific epithet, a compound noun in the genitive case, is derived from Betula nigra , from which the type series was reared.

Figures

FIGURE 1 – 3. Agrilus betulanigrae MacRae, n. sp., holotype male (lines = 1 mm). 1) Habitus; 2) genitalia (dorsal view); 3) lateral view.