Branchus geraceorum, Steiner, Warren E. & Jr, 2006

Steiner, Warren E. & Jr, 2006, New species of darkling beetles (Coleoptera: Tenebrionidae) from San Salvador Island, Bahamas, Zootaxa 1158, pp. 1-38 : 10-14

Branchus geraceorum , new species

( Figs. 4 A–F)

Description

Holotype, MALE: Body color very dark brown except elytral sutural carina blackish; outline oval ( Figs. 4 A–B), nearly continuous except for slight emargination between posterior angle of pronotum and elytral humerus; form convex, about equally so dorsally, ventrally; body length 14.2 mm, greatest width 7.8 mm at basal 1/3 of elytra; dorsum dull (except for raised polished elytral carinae), covered with fine, decumbent, pointed, tapered, golden brown setae ( Fig. 4 C).

Head less than ½ as wide as pronotum, widest at eyes and equally so at epistomal canthi; frons with triangular concavity across middle. Antenna with segment 3 slightly shorter than combined length of segments 4 and 5; segments 9, 10, 11 wider than long, forming weak club. Mentum broadly heart­shaped, without sharp angles; surface flat, punctuate except for polished anteromedian area, punctures bearing minute setae. Gena slightly produced anteriorly, not extending to half length of mentum.

Prothorax about twice as wide as long, broadest at basal 1/3, sides evenly arcuate, anterior margin broadly, evenly emarginate, anterior, posterior angles produced, the latter with rounded, flattened apices directed posteriorly; lateral margin very slightly explanate, with very fine polished bead on dorsal side of edge (often obscured by scalelike setae) and dense row of oblique overlapping scalelike setae on edge; pronotum evenly convex, surface with shallow rounded punctures, many contiguous, each with flattened blunt scalelike seta extending only to posterior margin of puncture (in most cases, but some closer to margins extend slightly beyond puncture edge); punctures absent along narrow smooth midline, on small, slightly raised areas on middle of each side of disk; ventral surfaces sparsely punctate laterally, more densely so medially, most dense, fine on prosternal process, with setae slender, hairlike, curved, nearly erect, very dense, fine, golden on prosternal process.

Thoracic ventrites somewhat polished, with deep, rounded, setiferous punctures large, scattered laterally, small, very dense medially, with dense golden setae as on prosternal process; Legs polished, with scalelike setae especially on tibiae; more hairlike on femora, forming relatively dense patches on flat ventral surfaces; tibial spurs well developed. Protibia broad, truncate at apex, forming a tooth at outer angle; apical half of anterior edge bearing row of short, sharp spines. Meso, metatibiae expanded at apex; metatibia feebly arcuate. Tarsi with conspicuous golden setae on ventral surfaces, the patches divided medially.

Elytra widest near basal 3/5ths, about 2.5 times longer than wide; surface generally smooth except for five raised, polished carinae ( Figs. 4 A, 4C) on disk and a sutural carina, latter extending to apex of elytron but very narrowed to apex; first, third, fifth discal carinae less prominent at elytral base; second, fourth carinae more raised at elytral base; third, fifth carinae longest, tapering, extending to about apical one­third of elytron; other carinae becoming narrow, broken toward mid­length of elytron. Scalelike setae similar to those on pronotum but more elevated, decurved, arising from very inconspicuous punctures, distributed sparsely, evenly on interval surfaces but more closely spaced, in a row along each side of carinae ( Fig. 4 C). Margin of pseudepipleuron well defined basally (with scalelike setae more dense than on elytral disk), becoming obscure at about apical one­fourth of elytron; scalelike setae on pseudepipleron similar in size, arrangement to those of elytral disk. Epipleuron long, tapered to elytral apex, generally 1/4th as wide as pseudepipleuron but abruptly widened at base, without setae except for a few along edge; apical part (opposite abdominal ventrites 4 and 5) forming a smooth groove between beaded edges. Abdominal sternites polished, with large punctures laterally; punctures absent in median areas of abdominal sternites 1–4 except on intercoxal process; sternite 5 with punctures less dense medially. Tegmen ( Figs. 4 D–E) 5 mm long, with apical piece longer than basal piece, flattened, truncate at apex, sinuate across apex with asymmetric edge between sharp, lateral projections. Median lobe with slender arching rodlike apex, ending with bulbous tip ( Fig. 4 F).

FEMALE. Similar to male but averaging larger, more robust, inflated. Secondary sexual differences include lack of the arcuate form of the hind tibia, relatively reduced setose flat ventral surfaces on the meso­, metatibiae, and more convex abdominal sternites.

Va r i a t i o n

Specimens range from 12.5 to 15.5 mm long. Some specimens have a soil encrustation that obscures some of the punctures and setae.

Material examined

“ BAHAMA ISLANDS: San Salvador, Sandy Point, 23°58’N, 74°33’W, 19 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (Holotype and 24 paratypes); same data except “ 17 February 2004 (2 paratypes); same data except “ 25 June 2005 / W. E. Steiner, J. M. Swearingen & D. J. Lodge, collectors” (3 paratypes); “ BAHAMA ISLANDS: San Salvador, near Altar Cave, 23°59’N, 74°32’W, 19 February 2004 / W. E. Steiner, J. M. Swearingen & S. Voegeli collectors” (1 paratype); “ BAHAMAS, SAN SALVADOR, 19 JUNE 1999, M. & L. DEYRUP / YELLOW BOWL TRAP, COPPICE FOREST SOUTH OF BAHAMIAN FIELD STATION” (1 paratype, ABSC); “ BAHAMAS: San Salvador Is., Dump, 13 Feb 1982, N. B. Elliott (1 paratype, GRCC); same data except “ 17 Jan 1982 ” (1 paratype, GRCC); “ BAHAMA ISLANDS: San Salvador, East Beach, 24°06’N, 74°25’W, 22 June 2003 / W. E. Steiner & J. M. Swearingen, collectors” (6 paratypes); same data except with the label “Reared from larva found 22 June 2003; pupated 19 Nov., eclosed 4 Dec., preserved 22 Dec. ’03” (1 paratype, with associated larval and pupal exuviae in gelatin capsule); same data except “ 18 February 2004 ” (8 paratypes); “ BAHAMA ISLANDS: San Salvador, Long Bay (Columbus Landing), 24°02’N, 74°31’W, 18 February 2004 / J. Winter, et al. collectors; in loose fine sand in weedy gap, coastal forest” (1 paratype); “SAN SALVADOR, BAHAMAS, 17 JUNE 1993, M. DEYRUP / THICK COPPICE­FOREST, HILL TRAIL NORTH OF OSPREY POND ” (1 paratype, ABSC); “ BAHAMA ISLANDS: San Salvador, North Point, near Govt. Dock, 24°07’N, 74°26’W, 15 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (1 paratype); “ BAHAMA ISLANDS: San Salvador, 1 km S Rocky Point, 24°07’N, 74°31’W, 17 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (14 paratypes); “ BAHAMA ISLANDS: San Salvador, Sandy Hook, 23°58’N, 74°28’W, 20 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (3 paratypes); “ BAHAMAS: San Salvador, Sandy Point / J. H. Knowles coll., 26 VI 65 ” (1 paratype, FSCA; teneral, with damaged right elytron); “ BAHAMAS: San Salvador, 2.3 mi. E. Watling’s Castle, 30­XII­63, D. R. Paulson” (4 paratypes, FSCA; one mislabeled from Mexico by the same collector; that label inverted and new label added by WES). Additional non­paratypic specimen: “ BAHAMA ISLANDS: San Salvador, Long Bay (Columbus Landing), 24°02’N, 74°31’W, 16 February 2004 / W. E. Steiner, J. M. Swearingen, J. Winter, et al. collectors” (1 elytron only).

median lobe, oblique lateral view.

Diagnosis

Branchus geraceorum is distinct in having the raised, polished, elytral carinae. It also lacks large punctures on the elytral surfaces, present in all other known Branchus species. It is the largest known darkling beetle on San Salvador. A key to Branchus species will be provided in a future monograph of the group. Branchus geraceorum belongs to the “ floridanus group” ( Steiner 1991) that includes the type species, B. floridanus LeConte (1866) , illustrated by Triplehorn and Weems (1964) from southern Florida, and B. woodi LeConte (1866) from New Providence, B. saxatilis Steiner (2005a) and several other species to be described. All of the members of this group have the same distinctive form of the male genitalia, with minor variations; the external characters are more useful for recognizing the species.

Etymology

The specific name honors Donald and Kathy Gerace, founders of the Gerace Research Center (formerly the Bahamian Field Station), San Salvador, in recognition of their contributions to science, education and conservation. The name is formed by a combination of the proper name “Gerace” + the Latin plural possessive ending, “­orum.” Habitats and collection notes

Specimens of this Branchus had been known to me for a number of years, borrowed from a few U.S. museums for an ongoing revision, and recognized as an undescribed, distinct species probably endemic to San Salvador. Having only a few specimens, most in poor condition, recent efforts were made to collect more of the beetles on two visits to the Gerace Research Center, examining the optimum habitats for these beetles ( Steiner 1991, 2005a) at several sites around the island, with success. Specimens were collected under leaf litter, palm thatch and wood debris on high sandy ground behind the beach strand, in sites partly shaded by shrub or small tree canopy, e.g. Bursera , Coccothrinax , Coccoloba on deep, coarse, coral sand. At Sandy Point, the type­locality; specimens were found in the greatest number and concentration, co­occurring with the larger of each of the two Diastolinus and Trientoma species described in this paper, at edges of light gaps in dry sites but under larger accumulations of palm thatch and leaf litter. Beetles are usually exposed at the sand surface but nestled in small depressions or sometimes immediatlely under the sand surface. Associated larvae (to be described in a future work) occur deeper in the sand, usually 2–6 cm, and are often found in greater numbers than adults. In June 2005, larvae were also found in fine sand under mixed leaf litter in swales of the hardwood forest interior behind the GRC.

Figures

FIGURE 4. Branchus geraceorum, new species, holotype. A, dorsal view; body length 14.2 mm. B, same, ventral view. C, detail of dorsum including scutellum and elytral suture. D­E, male genitalia, dorsal and lateral views, respectively; length of tegmen 5 mm. F, apical piece and apex of