Nautes guanahani, 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 : 29-32

Nautes guanahani , new species

( Figs. 9 A–D)

Description

Holotype, MALE: Body length 5.6 mm; greatest width (at basal 1/4th of elytra) 2.4 mm; ovoid ( Figs. 9 A–B), parallel­sided along mid­length of elytra; color dark brown with a very faint metallic purplish luster; surfaces finely alutaceous, not shining; antennae, maxillary palpi, tarsi light brown.

Head with shallow transverse depression between frons and clypeus; surface with punctures separated by as much as diameter of a puncture but some coalesce. Antennae 2.8 mm long; third antennomere longer than the first two combined.

Prothorax transverse, with evenly rounded sides, slightly narrower at base than front, narrower than elytra at humeri; pronotum with all margins beaded, slightly explanate laterally; pronotal surface evenly convex across disc, punctate; punctures separated by less than the diameter of a puncture, some are elongated and coalesce, except medially, where punctures are larger, more widely spaced. Prosternum densely punctate with many punctures coalesced; propleura with fine longitudinal wrinkles, not punctate. Metasternite somewhat polished medially; punctures separated by more than their diameters across middle, becoming indistinct, sparser toward sides.

Legs with surfaces punctate, very finely setose; front, middle tarsi with tarsomeres 1–3 broadened, with densely setose adhesive pads. Hind tarsi about 3/5ths as long as hind tibiae; basal tarsomere as long as the second and third combined.

Elytra with sides nearly parallel from basal 1/6th to apical 1/3rd, then evenly rounded and narrowed to apices; strial punctures moderately large, elongate and closely spaced, often coalescing; intervals convex, with scattered small punctures. Epipleurae impunctate; of even width along most of mid­length, then narrowed opposite 4th abdominal sternite (where surface becomes concave) to a point opposite corner of fifth sternite.

Abdomen with sternites appearing polished medially; punctures of this region distinct, separated by distances subequal to their diameters; punctures of alutaceous lateral areas smaller. First, second sternites with areas of median 1/5th flat to slightly concave; these areas with smaller, denser punctures bearing conspicuous golden setae directed posteromedially. Sternites 3–5 evenly convex across middle. Tegmen ( Figs. 9 C–D) 2 mm long; narrow, widest at about apical 1/4th of basal piece; apical piece in dorsal view with sides slightly convex, evenly narrowed to a rounded apex. Ratio of length of apical piece to basal piece 1:2.5.

FEMALE. Similar to male except: Front, middle tarsi basal 3 tarsomeres not expanded, without dense adhesive pads; abdominal sternites 1, 2 evenly convex, punctate across middle, without flattened setose areas.

Material examined

“ BAHAMA ISLANDS: San Salvador, Gerace Research Ctr., 24°07’N, 74°26’W, 21 June 2003 / W. E. Steiner & J. M. Swearingen collectors” (holotype); same data except “ 18 February 2004 ” (1 paratype, female). Other non­paratypic specimens: “ BAHAMA ISLANDS: San Salvador, Sandy Hook, 23°58’N, 74°28’W, 20 February 2004 / W. E. Steiner & J. M. Swearingen, collectors” (1 hind body); “ BAHAMA ISLANDS: San Salvador, Gerace Research Ctr., 24°07’N, 74°26’W, 23 June 2005 / W. E. Steiner & J. M. Swearingen collectors” (1 pair of elytra).

Va r i a t i o n

The female paratype is 6.4 mm in length; female Helopini are generally larger than males and both sexes are known to vary widely in size. The elytra of the non­paratypes are both smaller and larger than those of the types, with an elytral length ranging from 3.7–5.7 mm.

Diagnosis

The dull luster of most body surfaces of N. guanahani will separate it from the closely related N. azurescens (J. du Val) which has several color forms in Cuba, Florida, and Grand Bahama ( Steiner 2005a). While the male genitalia are very similar between the two species, external features are distinct; specimens of N. azurescens are consistently polished, often metallic green to blue, and generally larger in size. In N. guanahani the appendages are relatively shorter and thicker, punctures of the pronotum and head are larger and closer, some coalescing, and the body form is slightly more robust. Other species to be described, however, are known from other islands; those from dry scrub habitats tend to be smaller, darker, with dull surfaces, and may be flightless.

Distribution

Nautes guanahani is known only from San Salvador Island and is presumably endemic. Hind wings are present, but it is not known if this species can fly; the related N. azurescens does fly. No other Helopini are known from San Salvador.

Habitats and collection notes

The holotype was on a cement wall in open sandy turf of the GRC, found after dark under artificial lights. The female paratype was taken at night under loose dry bark on a dead standing trunk of Terminalia , where fragments of other specimens were noted; the pair of elytra listed above was collected in the same manner at this site. The hind body found at Sandy Hook was among Coccothrinax litter on sandy flats behind the beach. The scarcity of specimens may be due to a narrow season of emergence at a different time of year than sampled.

Figures

FIGURE 9. Nautes guanahani, new species, holotype. A, oblique lateral view; body length 5.6 mm. B, same, dorsal view. C­D, male genitalia, dorsal and lateral views, respectively; length of tegmen 2 mm.