Philonthus (Piezarthrus) plasoni Bernhauer, 1902

Hromádka, Lubomír & Janák, Jiří, 2011, Philonthus hapalemur sp. nov. and redescription of P. plasoni from Madagascar (Coleoptera: Staphylinidae: Philonthina), Acta Entomologica Musei Nationalis Pragae 51 (1), pp. 137-143 : 141-142

Philonthus (Piezarthrus) plasoni Bernhauer, 1902

( Figs 10–13 )

Philonthus plasoni Bernhauer, 1902: 166

Type locality. Madagascar, Fort Dauphin.

Type material. SYNTYPE: J, ‘Port Daufin [= Fort Dauphin], Madagaskar, von Dr Plason’ ( FMNH).

Description. Body length 8.1–8.3 mm, length of fore body (to the apex of the elytra) 4.7–5.0 mm. Head and pronotum black with golden iridescence, clypeus narrowly yellowish brown along anterior margin and antennal sockets, elytra and abdomen blackish brown, maxillary and labial palpi yellowish brown, mandibles brown yellowish, antenna black with antennomeres 1, 2 and 11 lighter, brownish, base of antennomere 2 lighter, femora and tarsi brown yellowish, tibiae darker.

Head transverse, wider than long (w/l ratio 1.36/1.64 = 1.21), sides parallel just behind eyes and than slightly narrowing posteriad. Eyes slightly convex, shorter than temples (eye length/temple length ratio 0.44/0.60 = 0.73). Area between eyes with 4 coarse punctures, distance between medial punctures three times larger than distance between medial and lateral puncture. Posterior angles slightly rounded with one puncture bearing long black seta. One coarse puncture situated near posterior margin of eyes. Temporal area almost impunctate. Surface with very fine, dense microsculpture consisting of transverse waves.

Antennae slender, moderately long, reaching to posterior third of pronotum when reclined. Relative length of antennomeres: 1 = 0.40; 2 = 0.24; 3 = 0.28; 4 = 0.20; 5 = 0.18; 6 = 0.16; 7 = 0.14; 8–10 = 0.12; 11 = 0.26.

Pronotum wider than long (w/l ratio 1.60/1.52 = 1.05), anterior angles almost rectangular with short black setae, lateral margins with several setae of variable length. Each dorsal row with 5 coarse punctures, punctures 2, 3, 4 equidistant, distance between punctures 1–2 and 4–5 slightly larger. Each sublateral row with 2 finer punctures, punctures 1 on the same level as punctures 3 in dorsal row. Microsculpture similar to that on head.

Scutellum finely, moderately sparsely punctate, punctures somewhat larger than eye facets, average distance between punctures as large as their diameter.

Elytra wider than long (w/l = 1.96/1.84 = 1.07), narrowest at midlength, very slightly widened anteriad and posteriad. Punctation sparser and coarser than that on scutellum. Punctures slightly larger than eye facets, separated on average by about one puncture diameter, on some places by one and half puncture diameter. Surface without microsculpture. Setation brownish yellow.

Abdomen wide, slightly narrowed from fifth visible tergite towards apex. Punctation at base of each segment coarser and denser than on elytra, becoming finer and sparser towards posterior margin of each tergite, surface without microsculpture, setation similar to that on elytra.

Legs. Tarsi Piezarthrus -like, with meso- and metatarsomeres distinctly flattened and dilated, relative length on metatarsomeres: 1 = 0.28; 2 = 0.16; 3-4 = 0.14; 5 = 0.32.

Male. Protarsomeres 1–3 dilated, each covered with modified pale setae ventrally, protarsomere 4 much narrower than the preceding ones. Sternite VIII slightly emarginated posteriorly, sternite IX as in Fig. 13 . Aedeagus ( Figs. 10–12 ) with median lobe distinctly, evenly widened anteriad, with broadly rounded apex; paramere long, distinctly bent towards median lobe, separated in two lobes, apical part of each lobe with about 3 sensory peg setae ( Fig. 12 ).

Female. Unknown to the authors.

Distribution. Madagascar: Fort Dauphin.

Discussion. LECOQ (1998) defined the subgenus Piezarthrus Lecoq, 1998 as follows: ‘The basic common character of these species is flattening and enlargement of meso- and metatarsi’. Philonthis plasoni shares this character as well, therefore it is transferred to that subgenus. Eight species were placed in this subgenus – seven from Madagascar and one from the Comoros. The dorsal row of the pronotum consists of 4 ( P. pollux Fauvel, 1905 ) or 5 large punctures (remaining species). For most of the species of this subgenus the hitherto available material is very poor – only 1– 2 specimens for most species. Philonthus plasoni is similar to P. humbloti Lecoq, 1998 described from the Comoros in the body length and the relative length of eyes, but it differs from the latter in the very widely rounded apex of the median lobe of the aedeagus and parallel lobes of the paramere.

Figures

Figs 10-13. Philonthus plasoni Bernhauer, 1902. 10 – aedeagus, ventral view, 11 – aedeagus, lateral view, 12 – apex of paramere with sensory peg setae, ventral view, 13 – male sternite IX. Scales: 0.5 mm (10, 11, 13) and 0.25 mm (12).