Diastolinus

Steiner, Warren E. & Jr, 2006, New species of darkling beetles (Coleoptera: Tenebrionidae) from San Salvador Island, Bahamas, Zootaxa 1158, pp. 1-38 : 25-29

Diastolinus that, new species

( Figs. 7 B, 7D, 8B, 8D)

Description

Holotype, MALE: Body length 8.1 mm; greatest width (at about basal 2/5ths of elytra) 3.5 mm.; robust, elongate­oval in outline ( Figs. 7 B, 7D); color black with appendages very dark brown to black; antennal apex and tarsi brown; surfaces feebly shining, alutaceous, with very minute short golden setae.

Head with frons, clypeus evenly convex; surface with very small punctures separated by two to four times diameter of a puncture, more closely spaced near epistomal margin. E yes small, ventral half smaller than dorsal, divided by about 1/2 the width of the ventral half of eye. Antennae 2.1 mm long; third antennomere as long as the first two combined; antennomeres 1–8 dark brown; antennomeres 9–11 light brown to yellowish; antennomeres 10, 11 of equal width.

Prothorax transverse, as wide as elytra at humeri, widest at posterior corners; sides nearly straight, gradually converging base to apical 2/5ths, then narrowing to rounded apical corners; apical margin evenly, broadly concave; basal margin strongly sinuate from sides to middle, with corners produced postteriorly. Pronotum with all margins narrowly beaded except for middle of anterior margin where bead becomes obsolete; pronotal surface evenly convex across disc, very finely punctate; punctures inconspicuous, separated by about three to five times diameter of a puncture, being closer, slightly larger laterally. Ventral surfaces of prothorax feebly rugose, impunctate; prosternal process lanceolate, with a feeble median carina. Mesosternum punctate­rugulose; metasternite genrally smooth, alutaceous except for polished, narrow, median longitudinal furrow.

Legs with surfaces finely punctate, setose. Front tibia gradually widened from base to obliquely truncate apex; margins feebly arcuate; posteroventral surface with stout setae in apical 2/3rds. Front middle tarsi with tarsomeres 1–3 broadened, with densely setose adhesive pads; front tarsomere 2 most dilated but less than twice as wide as long. Hind tarsi nearly as long as hind tibiae; basal tarsomere slightly longer than the second, third combined.

Elytra with sides evenly arcuate from humeri to apices; striae very slightly impressed; strial punctures small, not deep, polished at center, often irregularly spaced; intervals very feebly convex, without visible punctures; minute golden setae barely visible on intervals. Epipleurae appearing smooth; width narrowing from humerus to elytral apex, edges meeting in a narrowly rounded end.

Abdomen with sternites finely punctate; sternites 1–3 feebly longitudinally rugose; sternites 1 and 2 with slight concavities medially. Sternite 5 with a flattened area medially; posterior margin evenly rounded. Tegmen 2.5 mm long; strongly arched dorsally, widest at about mid­length of basal piece, narrowing apically and with small emargination at junction of basal and apical piece; apical piece in dorsal view ( Fig. 8 B) with sides sinuate; parameres becoming divided near basal 1/4th, narrowed abruptly in apical 1/4th to narrowly rounded, close apices, in lateral view distinctly undulate with sharp, flattened, upturned tips ( Fig. 8 D). Ratio of length of apical piece to basal piece 3:7.

FEMALE. Similar to male except: Front and middle tarsi with basal 3 tarsomeres not expanded, without dense adhesive pads; front tarsi with tarsomeres not much wider than long; abdominal sternites 1 and 2 with small flat area across middle, not concave; abdominal sternite 5 evenly convex, with apex truncate to shallowly emarginate for about 1/5th the width of sternite; at emargination, surface of sternite is abruptly deflexed, the marginal bead becomes obscured.

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 7 paratypes); same data except “ 17 February 2004 (8 paratypes); same data except “ 25 June 2005 / W. E. Steiner, J. M. Swearingen & D. J. Lodge, collectors” (9 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” (12 paratypes); “ BAHAMA ISLANDS: San Salvador, Barkers Point, 24°07’N, 74°29’W, 24 June 2005 / W. E. Steiner, J. M. Swearingen et al. collectors” (2 paratypes); “ THE BAHAMAS, San Salvador Island, CCFL VI­ 9­1978, A. G. Scarbrough (1 paratype, MAIC); same data except “Rd. N. CCFL, 1­ VI­ 1980 ” (1 paratype, MAIC); same data except “Rd. S. CCFL, 5­ VI­ 1980 ” (1 paratype, MAIC); “ THE BAHAMAS, San Salvador Island, 8 Dec. 1979 / Crest Site / D. Dowling” (3 paratypes, GRCC); “ BAHAMA ISLANDS: San Salvador, Dim Bay (beach) near Fortune Hill, 24E02’N, 74E26’W, 18 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (2 paratypes); “ BAHAMAS: San Salvador Is., Dump, 24 Feb 1982, N. B. E lliott (1 paratype, GRCC); “ THE BAHAMAS, San Salvador Island, 6 June 1978, P. Salbert / DUMP ” (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” (7 paratypes); same data except “ 18 February 2004 ” (4 paratypes); “ THE BAHAMAS, San Salvador Island, 7 Dec. 1976 / Farquharson Plantation, G[name illegible]” (1 specimen, prothorax and head only, GRCC); “ BAHAMA ISLANDS: San Salvador, French Bay Beach, 23°57’N, 74°32’W, 21 June 2003 ” (13 paratypes); same data except “ 17 February 2004 ” (9 paratypes); “ BAHAMA ISLANDS: San Salvador, Gerace Research Ctr., 24°07’N, 74°26’W, 19 June 2003 / W. E. Steiner & J. M. Swearingen collectors” (2 paratypes); same data except “ 20 June 2003 ” (5 paratypes); same data except “ 14 February 2004 ” (4 paratypes); same data except “ 19 February 2004 ” (3 paratypes); same data except “ 20 February 2004 ” (2 paratypes); same data except “ 23 June 2005 ” (2 paratypes); same data except “ 26 June 2005 ” (4 paratypes); “ BAHAMA ISLANDS: San Salvador, Green Cay, 24°09’N, 74°30’W, 26 June 2005 / W. E. Steiner, J. M. Swearingen et al. collectors” (15 paratypes); “ BAHAMA ISLANDS: San Salvador, Grotto Beach, 23°59’N, 74°32’W, 19 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (6 paratypes); “ 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” (8 paratypes); “ 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” (4 paratypes); “ THE BAHAMAS, San Salvador Island, Dec. 1976 / Near Polaris, S. Claflin” (1 paratype, GRCC); same data except “ Nov. 28, 1977 / T. Shlothauer” (1 paratype, GRCC); same data except “M. Pearson” (1 paratype, GRCC); same data except “ 23 Nov. 1978, S. Halwick, leg.” (1 paratype, GRCC); same data except “ 28 Nov. 1978 / D. Dowling” (1 paratype, GRCC); same data except “D. Horner” (1 paratype, GRCC); same data except second label (collector name?) illegible (1 paratype, GRCC); “ BAHAMA ISLANDS: San Salvador, Rice Bay (beach), 24°07’N, 74°26’W, 16 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (2 paratypes); “ 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” (15 paratypes); “ BAHAMA ISLANDS: San Salvador, Sandy Hook, 23°58’N, 74°28’W, 18 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (25 paratypes); same data except “ 20 February 2004 ” (12 paratypes); “ THE BAHAMAS, San Salvador Island, [no other data] 24 Nov. 1975 / Shelly Metz” (1 paratype, GRCC); same data except “ 26 Nov. 1975 / Larry Weill” (2 paratypes, GRCC); same data except “ 27 Nov. 1975 / E. Pecker, K. Rapp” (2 paratypes, GRCC); same data except “P. Salbert” (2 paratypes, GRCC); same data except “ 1 Dec. 1975 / Shelley Metz” (1 paratype, GRCC); same data except “E. Pecker, K. Rapp” (1 paratype, GRCC); same data except “P. Salbert” (2 paratypes, GRCC); same data except “ 2 Dec.1975 / K. Rapp, E. Pecker” (2 paratypes, GRCC); same data except “ 5 Dec. 1975 / G Jamison” (2 paratypes, GRCC); same data except “ November 23, 1977 / N. Pearson” (1 paratype, GRCC); same data except collector label absent (1 paratype, GRCC); “ THE BAHAMAS, San Salvador Island, 2 Dec. 1976 / Watling’s Castle, S. I[name illegible], leg.” (1 paratype, GRCC); “ BAHAMA ISLANDS: San Salvador, White Cay, 24°10’N, 74°28’W, 26 June 2005 / W. E. Steiner, J. M. Swearingen et al. collectors” (31 paratypes).

Va r i a t i o n

Specimens range from 6.7–9.2 mm in length; the smallest are males, largest, females. Individuals of the series from White Cay are consistently smaller than those from mainland sites, with an average length of about 7.3mm.

Diagnosis

The larger size, antennal coloration, surface features of the ventral sclerites, and form of the aedeagus will serve to identify this species. The size range does not overlap with that of D. this. The pale antennal apex including 3 segments, with the 10th and 11th of equal width, will separate it from D. this, which has only the 11th segment brown and wider than the rest. The smooth dull luster of the ventral sclerites also makes D. that easy to separate from D. this, which has a more shining, punctate venter.

Etymology

The specific name, used as a noun in apposition, is the English pronoun used to refer to the more distant one, “that,” rather than “this,” the one nearby. Of the two Diastolinus species on San Salvador, D. this occurs at one’s feet at the beach, while D. that lives farther inland.

Distribution

Diastolinus that is known only from San Salvador Island and is probably endemic. Two Diastolinus species often co­occur on West Indian islands and in this case, both D. this and D. that have been found at the same localities, but show distinct microhabitat separation, as described below.

Habitats and collection notes

All specimens, referred to as “the larger Diastolinus ” in field notes, were collected under leaf litter, palm thatch and wood debris on high sandy ground behind the beach strand, usually in sites shaded by shrub canopy, e.g. Coccoloba uvifera . A few specimens were found under matted dead grass and debris along foundations of buildings at the Gerace Research Center. Diastolinus that is possibly the most common and abundant tenebrionid on the island, and was the only tenebrionid found on two offshore cays. It was common at all sites where Branchus geraceorum was found. On the relatively barren flats behind the beach at Sandy Hook, specimens were found nearly co­occurring with D. this, less than one meter apart, but D. this was limited to the open primary beach dune crest, while specimens of D. that were found under larger accumulations of leaf litter under and at edges of shrubs.

Figures

FIGURE 7. Two Diastolinus species, holotypes, imaged to scale with each other. A, D. this, new species, dorsal view; body length 6.6 mm. B, D. that, new species, dorsal view; body length 8.1 mm. C­D, same, ventral views, respectively.

FIGURE 8. Two Diastolinus species, holotypes, male genitalia imaged to scale with each other. A, D. this, new species, dorsal view; length of tegmen 2.1 mm. B, D. that, new species, dorsal view; length of tegmen 2.5 mm. C­D, same, lateral views, respectively.