Prosopeus Murray

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 : 13-18

Prosopeus Murray

TYPE SPECIES: Prosopeus subaeneus Murray, 1864: 331 (monotypy). Prosopeus Murray, 1864: 330 [n. gen.].

Brachypeplus: Sharp, 1878: 131 (syn. in part) [n. sp.].

Nesopeplus Sharp in Sharp & Scott, 1908: 474 [n. gen., n. spp.]. TYPE SPECIES: Brachypeplus protinoides Sharp, 1879: 85 (hereby desig.). Nesopetinus Sharp in Sharp & Scott, 1908: 492 [n. gen., n. spp.]. TYPE SPECIES: Brachypeplus discedens Sharp, 1878: 133 (hereby desig.). Prosopeus: Ewing, 2004: 33 [syn.].

Diagnosis: Size usually small, 2.3–5.5mm L, 1.125–2.0mm W. Color yellow to black, often with yellow to pale red markings at middle of each elytron, often metallic, from pale brassy or bronze to dark purple, microsculpture often very fine with surface subglabrous, rarely obsolete with surface glabrous; often pronotum and elytra convex, abdomen tapering evenly through segments 5,6, and 7.

Description: Head variable, eyes usually small, temple present or absent, usually forming an oblique angle with occiput; antennal grooves usually strongly convergent, distinct medially, defined laterally by impunctate strip; projecting portion of antennal groove with long setae laterally; labrum with 2–3 dorsolateral and 1–5 dorsomedial submarginal macro setae (sometimes dorsomedial submarginal only with one seta, missing other side); medial tooth usually prominent, rarely obsolete, rounded, narrowly emarginate laterally on either side, anterior margin sinuate to broadly curved and gently angled posteriorly, lateral angle broadly rounded, ventroapical setae forming two pairs of distinct tufts, shorter within emarginations, longer laterally before angle; mandibles bicuspid, 2–5 subapical teeth; 3rd labial palpomere transverse to subquadrate, usually slightly narrowed distally, sometimes distal and proximal widths subequal, medial margin weakly sinuate.

Prothorax transverse, little explanate, usually narrower anteriorly, rarely strongly sinuate and narrowed posteriorly, or trapezoidal; lateral margins evenly curved to strongly sinuate posteriorly; anterior margin weakly emarginate, nearly truncate, to convex; posterior margin convex and bi- or tri-sinuate; prosternal process narrow between coxae and small and sharply to moderately upturned posterad of coxae.

Margins of elytra narrowly explanate, elytral margin equal to 2x the width of the marginal bead or less at middle, rarely 3x at humeral angle; elytra shorter than abdomen, 1–3 abdominal segments at least partially exposed; surface of elytra usually regular; striae, when present, without raised areas; punctation of elytra variable, glabrous with few shallow regular punctures, punctures dense and confused, indistinctly striate, or distinctly striate. Pygidium of male truncate, broadly rounded, or emarginate, emargination shallow to deep with lateral margins forming blunt to sharp teeth.

FIGURES 4–8: Aedeagus and internal copulatory sac. 4. Brachypeplus (Selis) undescribed (Marquesas No. 1); 5. Prosopeus segnis ; 6. Prosopeus floricola ; 7. Cillaeopeplus reitteri ; 8. Cillaeopeplus undescribed (Kauai No. 1). aed aedeagus, fl flagellum, flex flexure between external membrane and flagellum, md membranous duct, prfl preduct flagellum, psfl postduct flagellum, sd sperm duct, sdj junction of spermduct and flagellum, sp sclerites-primary. Figs. 4–7 with dorsal surface of perisac up, fig. 8 with oblique ventral view, fig. 8 perisac inset as in 4–7.

Aedeagus of male with apical margins broadly rounded, apex acuminate; sides parallel to slightly wider apically or basally; perisac short, very little development distad of flagellum, sclerites-primary highly variable among species, usually strongly sclerotized and situated dorsally with sperm duct exiting dorsally, rarely ventral and internal; sperm duct exiting ventrally; membrane expanded dorsoventrally, dorsal and ventral distal incisions, when present, shallow and broad. Female gonocoxites from elongate to extremely reduced. Basal ring of spermatheca strongly sclerotized.

Prosopeus is the largest genus of endemic Hawaiian Nitidulidae with 55 described and at least 16 undescribed species. The genus was described by Murray (1864) for a mislabeled specimen which erroneously indicated Caffraria ( South Africa) to be the collection locality (Ewing 2004). When Sharp described the first specimens correctly associated with the Hawaiian Islands he placed them in the genus Brachypeplus ( Sharp, 1878) , later moving them to the genera Nesopeplus and Nesopetinus ( Sharp and Scott, 1908) . The only character used to divide the species between these genera was the shape of the prosternal process, with Nesopeplus having it sharply upturned and appressed to the postcoxal sclerites (figs. 22, 41) and Nesopetinus having it moderately upturned and presenting a short face in posterior view (figs. 23, 25).

The adults of Prosopeus can be found associated with fresh and decaying flowers, subcortically, in leaf axils, in decaying fruit, on both fresh and decaying vegetation, and rarely in leaf litter. None of the members of this group have reduced flight wings and are the only endemic Hawaiian sap beetles known to fly during the day when not disturbed. Many species are common in flowers, especially those of Clermontia , Lobelia , Trematolobelia , Ilex , Broussaisia , Hedyotis , Coprosma , Psychotria , Pleomele , Melicope , Acacia koa , Cheirodendron , Dubautia , Labordia , and Pittosporum . They can be found, at least rarely, on flowers of most tree and shrub species in native mesic and wet forests. They have been observed to consume nectar, mycelial fungi, yeasts, and pollen, with gut dissections confirming the latter two. Samples taken on Molokai, Maui, and Hawaii Island, have found yeasts in the genera Metschnikowia ( Lachance et al. 2003; Lachance et al. 2005). They can be locally common on many species of ferns with robust fronds and dense growth habit such as Ctenitis , Deparia , Diplazium , Dryopteris , and Cibotium .

The type for the synonymous genus Nesopetinus was invalidly designated by Sharp with the following statement in the original description "The type is a remarkably flat insect". He was clearly referring to Prosopeus (= Nesopetinus ) discedens ( Sharp 1878) , a distinctly flat species, being the first species described, with the next species, Prosopeus (= Nesopetinus ) tinctus ( Sharp 1879) , described the following year.