Eupetinus Sharp

Ewing, Curtis, 2007, Phylogenetic analysis of the genera of endemic Hawaiian sap beetles (Coleoptera: Nitidulidae) based on morphology with redescription and key to the genera of endemic Hawaiian Nitidulidae, Zootaxa 1427, pp. 1-36 : 23-25

Eupetinus Sharp

TYPE SPECIES: Brachypeplus impressus Sharp, 1878: 135 . (hereby desig.) Brachypeplus: Sharp, 1878: 131 (syn. in part).

Eupetinus Sharp in Sharp & Scott, 1908: 461 [n. gen., n. spp.].

Apetinus Scott in Sharp & Scott, 1908: 458 [n. gen., n. spp.].

TYPE SPECIES: Brachypeplus brevis Sharp, 1878: 137 (hereby desig.).

Diagnosis: Size usually small, 3.0–5.0 mm L: 1.5–2.0mm W. Third labial palpomere transverse, nearly always twice as wide at apex as long; medial margin strongly sinuate. Elytra with striae distinct, usually irregular, rarely nearly regular; interstices usually irregularly raised, raised areas often dilated, paler, and bearing tufts of setae. Color variable, from pale yellow to black, often distinctive with head dark or pale, pronotum pale with vague medial band, scutellum dark to very dark, elytra patterned with pale and dark markings; usually the margin and area adjacent to scutellum pale, remainder dark with pale marks associated with the interstices; from limited to raised and thickened pubescent areas to the entire length; dimidiatus form with entire distal portion of elytra pale ( Sharp &and Scott, 1908); abdomen often pale, entirely so most often in females, often with dark markings medially and along suture of paratergite; sometimes, most commonly in males, pattern well defined and strongly contrasted, tergites 5 and 6 dark with pale areas anteromedially and adjacent to spiracle, paratergite pale to dark with a gradient, darkest at posterior margin; pygidium as in other segments except wide pale areas along lateral margins. Microsculpture of dorsum usually granulate to fine lines, surface nearly always uneven, rarely microsculpture of fine lines and surface even and subglabrous.

Description: Eyes small, facets fine; genae with short temple behind eyes, rounded to sinuate behind, distinctly angled posterad to postgena. Antennal grooves short, weakly convergent, often margins weakly defined anterad and obsolete posterad; labrum with two pairs submarginal macrosetae, medial tooth broadly rounded, narrow emarginations immediately laterad with small tufts of setae, anterolateral margin sloping to form an obtuse angle with convex lateral margin; 3rd labial palpomere strongly transverse, 2x as wide as long, margin strongly sinuate medially, apex as wide as or wider than base.

Prothorax transverse; lateral margins smoothly curved or recurved and constricted posterad; anterior margin weakly to moderately emarginate, anterior angles broadly rounded, posterior margin weakly bisinuate; prosternal process little recurved and expanded posterad of coxae, apex subtruncate, broadly rounded, or shallowly emarginate; lateral margin smooth to weakly crenulate; posterior angle obtuse to sinuate.

Elytra less than 2x as long as wide, usually much shorter, from 1.8–1.5x; lateral margin more than 2x width of marginal bead, usually 4x–10x, widest at humeral angle. Punctures of elytra coarse, forming distinct striae. Interstices of elytra distinctly raised, often with raised and dilated areas than can be paler in color and possess extra rows of setae forming tufts on interstices 3, 5, and 7, sometimes with a slight dilated area in interstice 6. Surface of elytra usually appearing distinctly uneven, sometimes nearly even. Distal margin weakly to strongly bisinuate, longest laterally. Elytra exposing abdominal segments 7, 6, and part of 5.

Tarsal segments 1–3 with lobes dilated.

Pygidium of male shallowly and broadly emarginate, subtruncate, or broadly rounded. Anal sclerite usually narrow, apex acute, rounded, or subtruncate. Male perisac narrow and parallel-sided, sclerites-primary elongate, extending to distal apex; flagellum reduced, highly folded and fused to proximal apex of scleritesprimary; flagellum often with small lateral plate-like projections; ventral distal margin narrowly and acutely emarginate, dorsal distal margin weakly projecting and broadly rounded. Female pygidium subtruncate to broadly rounded. Gonocoxites elongate. Basal ring of spermatheca strongly sclerotized.

There are 29 described and at least nine undescribed species of Eupetinus . Apetinus was proposed by Scott for species with reduced flight wings. Apetinus is herein synonymized under Eupetinus . Many of the species in this genus are separated primarily based on the form of the elytral striae and the shape of the male anal sclerite. A single species will often have a high degree of intraspecific variation in these characters that broadly overlaps with other species with a similarly high rate of intraspecific variability. The species are often very difficult to separate based on external morphology, and genitalia are likewise very similar among all species. Eight of the 24 species described as being widespread, having populations on multiple islands, are from this genus. Most if not all of the separate island populations should be placed in a separate species-level taxon.

Many species have reduced flight wings and were placed in Apetinus by Sharp based primarily on this condition. Even fully winged species appear to be incapable of powered flight. When disturbed, individuals will occasionally spread their wings, but the author has never observed flapping or flight of any kind by a specimen of Eupetinus . Molecular data supports 8 or more separate lineages having reduced flight wings (Ewing 2005). In most cases the brachypterous species is found in leaf litter, almost exclusively Metrosideros leaves, and the sympatric, fully winged, putative sister species being arboreal on a variety of hosts including Metrosideros (Ewing 2005) .

Eupetinus species are found in wet and mesic forests in association with a large number of host plants. They are most often found in association with leaf and bark surfaces, decaying plant material, under bark, in leaf litter, on dead branches, droopy leaves, decaying fruit, in leaf axils, and fresh and decaying flowers. Most of the leaf and bark associated species are generalists, though a few are limited to one or two host plant species, whereas those associated with flowers, fruit, leaf axils, and leaf litter are usually limited to one or a few hosts.

The placement of Apetinus as a junior synonym of Eupetinus requires the following new combinations:

Eupetinus macrothorax (Scott) , n. comb.

Apetinus macrothorax Scott in Sharp & Scott, 1908: 459.

Eupetinus medius (Scott) , n. comb.

Apetinus medius Scott in Sharp & Scott, 1908: 459.

Eupetinus explanatus (Sharp) , n. comb.

Brachypeplus explanatus Sharp, 1879: 84 .

Apetinus explanatus: (Scott) in Sharp & Scott, 1908: 460.

Eupetinus brevis (Sharp) , n. comb.

Brachypeplus brevis Sharp, 1878: 137 .

Apetinus brevis: (Sharp) in Sharp& Scott, 1908: 460. Eupetinus pumilio (Sharp) , n. comb.

Apetinus pumilio Sharp in Sharp & Scott, 1908: 460.