Diastolinus

Steiner, Warren E. & Jr, 2006, New species of darkling beetles (Coleoptera: Tenebrionidae) from San Salvador Island, Bahamas, Zootaxa 1158, pp. 1-38 : 21-25

Diastolinus this, new species

( Figs. 7 A, 7C, 8A, 8C)

Description

Holotype, MALE: Body length 6.6 mm; greatest width (at about mid­length of elytra) 2.9 mm.; robust, broadly oval in outline ( Fig. 7 A); color black with appendages very dark brown to black; dorsal surfaces feebly shining, alutaceous; venteral surfaces more polished ( Fig. 7 C), with scattered golden setae.

Head with frons, clypeus evenly convex; surface with very small punctures separated by two to four times the diameter of a puncture, more closely spaced near epistomal margin. Eyes small, ventral half smaller than dorsal, divided by about 2/3rds width of ventral half of eye. Antennae 1.5 mm long; third antennomere shorter than first two combined; apical (11th) antennomere brown, paler in apical half; antennomere 11 globular, widest, more so than antennomere 10.

Prothorax transverse, as wide as elytra at humeri, with sides nearly parallel from base to mid­length, then converging to rounded apical corners; apical margin evenly, broadly concave; basal margin slightly sinuate from sides to middle. Pronotum with all margins narrowly beaded except for middle of anterior margin where bead becomes obsolete; pronotal surface evenly convex across disc, finely punctate; punctures separated by about three to five times diameter of a puncture, being closer, slightly larger laterally. Ventral surfaces of prothorax feebly rugose, with some punctures, more so medially; prosternal process lanceolate, more polished, raised laterally, medially with longitudinal ridges. Mesosternum densely punctate­rugulose; metasternite with coarse punctures,furrows medially; punctures becoming smaller, sparser between middle, hind coxae, then obsolete laterally, where surface becomes more alutaceous.

Legs with surfaces punctate, finely setose. Front tibia robust, gradually widened from base to obliquely truncate, broad apex; inner margin feebly arcuate, nearly straight along mid­length; outer margin feebly sinuate, posteroventral surface with stout setae in apical 2/ 3rds, especially dense along outer margin. Front, middle tarsi with tarsomeres 1–3 broadened, with densely setose adhesive pads; front tarsomeres 2, 3 most dilated, twice as wide as long. Hind tarsi about 4/5ths 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, lateral intervals bear minute golden setae. E pipleurae appearing smooth except for furrow parallel to marginal bead from about basal 1/3rd to near apex; width narrowing from humerus to elytral apex, ending in a single narrow polished edge.

Abdomen with sternites punctate, smooth medially except coarsely rugose on intercoxal process; sternites 1–3 feebly longitudinally rugose; sternites 1, 2 with slight concavities medially. Sternite 5 with a flat area apicomedially; posterior margin evenly rounded. Tegmen 2.1 mm long; strongly arched dorsally, widest at about mid­length of basal piece, narrowing apically, with small emargination at junction of basal and apical piece; apical piece in dorsal view ( Fig. 8 A) with sides sinuate, nearly parallel at middle for about 1/4th its length; parameres becoming divided near basal 1/5th, narrowed abruptly in apical 1/5th to narrowly rounded, close apices and in lateral view slightly undulate with sharp, flattened tips ( Fig. 8 C). Ratio of length of apical piece to basal piece 3:7.

FEMALE. Similar to male except: Front, middle tarsi with basal 3 tarsomeres not expanded, without dense adhesive pads; front tarsi with tarsomeres not much wider than long; abdominal sternites 1 an 2 with small flat area across middle, not concave; median flat area of abdominal sternite 5 smaller, indistinct, may be slightly concave apically.

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 11 paratypes); same data except “ 17 February 2004 (4 paratypes); same data except “ 25 June 2005 / W. E. Steiner, J. M. Swearingen & D. J. Lodge, collectors” (3 paratypes); “SAN SALVADOR, BAHAMAS, 14 June 1993, M. DEYRUP / Beach near BFS [= Bahamian Field Station]” (1 paratype, GRCC); “ 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 [=College Center of the Finger Lakes] VI­ 9­1978, A. G. Scarbrough (3 paratypes, MAIC); “ BAHAMA ISLANDS: San Salvador, Dim Bay (beach) near Fortune Hill, 24°02’N, 74°26’W, 18 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (4 paratypes); “ BAHAMA ISLANDS: San Salvador, East Beach, 24°06’N, 74°25’W, 18 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (7 paratypes); “ BAHAMA ISLANDS: San Salvador, French Bay Beach, 23°57’N, 74°32’W, 21 June 2003 ’ (19 paratypes); same data except “ 17 February 2004 ” (2 paratypes); “ BAHAMA ISLANDS: San Salvador, Gerace Research Ctr., 24°07’N, 74°26’W, 14 February 2004 / W. E. Steiner & J. M. Swearingen collectors” (2 paratypes); same data except “ 26 June 2005 / W. E. Steiner & J. M. Swearingen collectors” (9 paratypes); same data except 19–22 June 2003 / Yellow bowl pitfall trap among sparse plants on beach dune; collrs. W. E. Steiner & J. M. Swearingen” (1 paratype); “ BAHAMA ISLANDS: San Salvador, Grotto Beach, 23°59’N, 74°32’W, 19 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (3 paratypes); “ BAHAMA ISLANDS: San Salvador, Rice Bay (beach), 24°07’N, 74°26’W, 16 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (3 paratypes); “ BAHAMA ISLANDS: San Salvador, Sandy Hook, 23°58’N, 74°28’W, 20 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (16 paratypes); “ BAHAMA ISLANDS: San Salvador, Target Beach, 24°0’N, 74°32’W, 25 June 2005 / W. E. Steiner, J. M. Swearingen et al. collectors” (4 paratypes); “SAN SALVADOR, BAHAMAS, 18 June 1993, M. DEYRUP / ON BEACH, 3 DOG SITE ” (3 paratypes, GRCC); “ THE BAHAMAS, San Salvador Island, [no other data] Nov. 27, 1975 / Steven Young” (1 paratype, GRCC); same data except “ Dec. 2, 1975 ” (1 paratype, GRCC); same data except “ 2 Dec. 1975 / Rick Hopkins” (1 paratype, GRCC).

Va r i a t i o n

Specimens range from 5.6–6.6 mm in length; the smallest are males, largest, females.

Diagnosis

The robust body and relatively stout legs, antennal coloration, surface features of the ventral sclerites, and form of the aedeagus will serve to identify this species. A more detailed list of compared characters will be discussed following the description its other new congener, below. As discussed in previous works ( Steiner 2005a, 2005b) the genus needs redefinition and may be considered a complex of circum­Caribbean species groups under Blapstinus . Flight wings are vestigial and elytra are fused; the metasternite is short, with middle and hind coxae separated by less that the diameter of a coxa.

Etymology

The specific name “ this ” is from the Greek word meaning “shore” or “beach” in reference to the habitat of the beetle, discussed below. The name is used as a noun in apposition.

Distribution

Diastolinus this is known only from San Salvador Island and is probably endemic. Closely related forms are known from islands of some of the other Bahamian Banks.

Habitats and collection notes

All specimens, referred to as “the smaller Diastolinus ” in field notes, were collected along the edge of the upper beach strand on pure sand under dry deposits of leaf litter or under low spreading plants. Specimens from Sandy Point were on wide, open beach dunes with sparse vegetation, sometimes clustered under isolated small plants with winddeposited litter at the base.

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.