Trientoma voegeliorum, 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 : 8-10

Trientoma voegeliorum , new species

( Figs. 1 C–D, 2B, 3C–D, 3F)

Description

Holotype, MALE: Body length 6.2 mm; greatest width 2.7 mm (at about basal 2/5ths of elytra); robust, elongate­oval in outline ( Fig. 1 C–D, 3F), with pronoto­humeral margin nearly continuous; color black with appendages dark brown; surfaces feebly shining, alutaceous, with very minute short golden setae.

Head ( Fig. 2 B) with fused frons, clypeus evenly convex; surface with small punctures medially, becoming longitudinally rugose laterally but similarly punctate over epistoma; punctures separated by one to two times the diameter of a puncture; rugose area beginning at lateral clypeal invaginations, extending, widening posteriorly above eyes to point not far posterad of eye. Clypeus weakly trilobed, margin slightly produced medially, expanded laterally. Antennae 1.8 mm long; second antennomere (pedicellus) about 2/3rds as long as third antennomere; antennomere 10 widest, weakly clasping smaller apical antennomere.

Prothorax transverse, as wide as elytra at humeri, widest at posterior corners; sides feebly curved and gradually converging from base to narrowly rounded anterior corners; posterior, anterior margins smoothly sinuate from sides to middle, edges narrowly polished; posterior corners produced posteriorly. Pronotum with lateral margins narrowly beaded; surface evenly convex across disc, very slightly explanate at posterolateral corners, very finely punctate medially as on head, punctures becoming larger, elongate laterally, with some coalescing, appearing rugulose in lateral quarters of disk. Ventral surfaces of prothorax densely punctate except posterior third of episternum smoothed; punctures of varying size, separated by less than their diameters; prosternal process broadly lanceolate, with apex deflexed, surface flat, punctate as on prosternum. Mesosternum punctate as on prosternum but anterior punctures larger, more separated, median depression nearly impunctate, smooth; mesepimeron impunctate; metasternite with punctures more widely spaced than on prosternum, of varying size, from very fine medially to large, deep laterally.

Legs with surfaces finely punctate, sparsely setose. Front tibia widened from base to broad, truncate apex; margins feebly arcuate; dorsolateral edge with row of stout tooth­like setae. Tarsi unmodified; hind tarsi about 2/3rds as long as hind tibiae; basal tarsomere nearly as long as the remaining three combined.

Elytra with sides evenly arcuate from humeri to apices; striae not defined; surface smooth, imperceptibly punctate but with reticulate alutaceous luster; laterally with extremely small, fine golden setae. Epipleurae smooth; width narrowing abruptly from humerus to about basal 1/3rd, then gradually narrowing and becoming concave to narrowly grooved at elytral apex,.

Abdomen with sternites smooth, convex across middle but sternites 1 and 2 slightly flattened medially, minutely punctate except for sternite 1 which has scattered large punctures (similar to those on metasternite) basomedially, becoming smaller posteriorly. Tegmen 1.3 mm long; widest near base of basal piece ( Fig. 3 C), narrowing to sub­parallel along length of apical piece, then abruptly narrowing to a broadly rounded apex with small triangular median emargination (division of parameres); in lateral view ( Fig. 3 D) sinuate, with apical and basal piece arched dorsally but with dorsal emargination at junction; apex of parameres simple, broadly rounded. Ratio of length of apical piece to basal piece 14:11.

FEMALE. Similar to male except abdominal sternites 1 and 2 slightly less flattened medially (more evenly convex).

Material Examined

“ BAHAMA ISLANDS: San Salvador, Sandy Hook, 23°58’N, 74°28’W, 18 February 2004 / W. E. Steiner & J. M. Swearingen collectors” (holotype and 30 paratypes); same data except “ 20 February 2004 ” (13 paratypes); same data except “French Bay Beach, 23°57’N, 74°32’W, 21 June 2003 ” (1 paratype).

Va r i a t i o n

Specimens range from 5.3–6.7 mm in length; the smallest are males, largest, females.

Diagnosis

The smaller size, surface features, and form of the aedeagus will serve to identify this species. The size range does not overlap with that of its larger congener, T. jilae , which has a completely rugose frons and faint strial punctures.

Etymology

The specific name honors Vince and Sandy Voegeli of the Gerace Research Center, San Salvador, in recognition of their continuing logistic support and hospitality during fieldwork on the island. The name is formed by a combination of the proper name “Voegeli” + the Latin plural possessive ending, “­orum.”

Distribution

Trientoma voegeliorum is known only from San Salvador Island and is presumably endemic. Two Trientoma species often co­occur on West Indian islands but usually have differential habitat occurrence and differ in size and appearance. In this case, either T. jilae or T. voegeliorum were found to be dominant at a particular locality (i.e., rarely share the same microsite) behind beaches of the southern parts of the island.

Habitats and collection notes

All specimens 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 . It was found to be most abundant on the relatively barren flats behind the beach at Sandy Hook, the type­locality; specimens were found co­occurring with the larger Diastolinus species described in this paper, in open dry sites but under larger accumulations of palm thatch at bases of Coccothrinax argentata trunks and leaf litter at edges of shrubs.

Figures

FIGURE 1. Two Trientoma species, holotypes. A, T. jilae, new species, dorsal view; body length 9.3 mm. B, same, ventral view. C, T. voegeliorum, new species, dorsal view; body length 6.2 mm. D, same, ventral view.

FIGURE 2. Two Trientoma species, holotypes, oblique frontal views of heads, imaged to scale with each other. A, T. jilae, new species; head width at eyes 2.3 mm. B, T. voegeliorum, new species, head width at eyes 1.6 mm.

FIGURE 3. Two Trientoma species, holotypes, imaged to scale with each other. A­B, T. jilae, new species, male genitalia, dorsal and lateral views, respectively; length of tegmen 1.6 mm. C­D, T. voegeliorum, new species, male genitalia, dorsal and lateral views, respectively; length of tegmen 1.3 mm. E­F, dorsal views of T. jilae (body length 9.3 mm) and T. voegeliorum (body length 6.2 mm), respectively.