Diatrichalus Kleine, 1926

Bocek, Matej, 2017, New species of Diatrichalus (Coleoptera: Lycidae) from New Guinea and the Moluccas, Zootaxa 4247 (5), pp. 577-584 : 578-579

Diatrichalus Kleine, 1926

Diatrichalus Kleine, 1926: 167 . Type species: Diatrichalus xylobanoides Kleine, 1926: 167 (by original designation). = Mimotrichalus Pic, 1930: 92; Bocak, 1998: 193. Type species: Mimotrichalus tenimberensis Pic, 1930: 92.

Diagnosis. Diatrichalus share with other genera of former Trichalina (i.e. Flabellotrichalus Pic, 1921 , Trichalus , Eniclases Waterhouse, 1879 , and Microtrichalus Pic, 1921 ) the pronotum with only a single median areola of a variable shape, lateral pronotal carinae vestigial to completely absent, and the elytra with a shortened primary costa 1 ( Bocak 1998). Unlike them, the pronotum has a characteristic wide shape and lateral pronotal margins are often almost parallel-sided in the basal part with a protuberance in the basal third ( Figs 2–6 ). All Diatrichalus have acutely serrate antennae, similar to most Trichalus and Microtrichalus , but never have long lamellae known in Flabellotrichalus and some species of Trichalus and Eniclases . The phallus is robust, completely sclerotized, without the extensive membranous part known in other trichaline genera. The internal sac is extensively sclerotized and partly exposed from the tube of the phallus. Paired accessory thorns are absent from the internal sac unlike numerous other metriorrhynchine net-winged beetles. Although subtle, the external characters are usually sufficient for generic identification, but the shape of male genitalia is essential in some cases ( Figs 7–24 ).

Diatrichalus was originally proposed only for species with absent secondary elytral costae, i.e., only four longitudinal costae were present in each elytron. The current concept is much wider and includes species with secondary elytral costae present or absent ( Bocak 2001).

Redescription. Body medium-sized, most species uniformly black ( Fig. 3 ), some species with metallic shine of thorax and abdomen ( Figs 4–5 ), occasionally with metallic blue elytra; only a few species with brightly colored pronotum and elytra, usually yellow, reddish or orange pronotum and humeral part of elytra ( Figs 2, 6 ).

Head small, hypognathous, partly covered by pronotum, cranium without rostrum, eyes hemispherically prominent, variable in size ( Figs 2–6 ). Mouthparts well developed, with robust palpi and short, robust mandibles. Antennae flattened, acutely serrate in both sexes. Pronotum trapezoidal, always considerably wider than long, with single distinct median areola along midline, lateral carinae absent; lateral pronotal margins elevated. Scutellum emarginate at apex. Elytra flat, primary costae 2…4 well developed in at least four fifths of elytral length, costa 1 always shortened, reaching about one fifth of elytral length, costa 2 and 3 often fused at apical part, costa 3 slightly shortened in some species; secondary costae well developed to absent in some species (e.g. D. manokwarensis sp. n., Fig. 3 ). Legs compressed, strong, moderately long.

Male genitalia with robust phallus, apical part widened and often ventrally projected, apical part of internal sac sclerotized, phallobasal membrane never sclerotized ( Figs 7–24 ). The detailed morphological description of Diatrichalus and related genera was published by Bocak (2001).

Distribution and diversity. The highest diversity of Diatrichalus is known from New Guinea where the genus is represented by 28 species ( Fig. 1 ; Bocak 2001); another 3 spp. are known from Australia, 3 spp. from the Moluccas, 4 spp. from the Solomon Islands, 1 spp. from Sulawesi and 5 spp. have been described from the Philippines ( Bocak 2000a). Only D. niger Waterhouse occurs in the Malay Peninsula, Sumatra and Borneo ( Fig. 1 ). The species from the Solomon Islands are omitted from the map.

Figures

FIGURE 1. Distribution and diversity of Diatrichalus (the numbers of recorded species in each region including the newly described species).

FIGURES 2 – 6. General appearance of Diatrichalus. 2 — D. buruensis sp. n., male; 3 — D. manokwarensis sp. n., male; 4 — D. mindikensis sp. n., male; 5 — D. robustus sp. n., male; 6 — D. mancus, male. Scales 2 mm.

FIGURES 7 – 24. Male genitalia (ventral and lateral views, respectively). 7, 8 — D. buruensis sp. n.; 9, 10 — D. manokwarensis sp. n.; 11, 12 — D. mindikensis sp. n.; 13, 14 — D. robustus sp. n.; 15, 16 — D. mancus; 17, 18 — D. dilatatus; 19, 20 — D. sinuaticollis; 21, 22 — D. xylobanoides; 23, 24 — D. niger. Scales 0.5 mm.