Subgenus Microgeniatum Rivalier, 1970

Pogonostoma (Microgeniatum) Rivalier, 1970: 306 (partim).

Pogonostoma (Microgeniatum): Moravec 2007: 447.

Type species: Pogonostoma pseudominimum W. Horn, 1934 (by original designation).

Revised differential diagnosis. Because of their extremely small to small, 5.4–7.5 mm long, black bodies, and 4–setose labrum, the four known species of the subgenus Microgeniatum may resemble some species of the subgenus Microstenocera Jeannel, 1946. However, in contrast to the irregular elytral setal vesture in Microstenocera, the species of Microgeniatum are characterized by their regular elytral setal vesture, consisting of ornamental se- tae, which are confined to punctures—each ornamental seta (microtrichia) arising from anterior margin of corre- sponding puncture (as in the nominotypical subgenus, which, however, houses species with much larger body with multisetose labrum). Elytra shiny black, notably coarsely punctate throughout, with smooth, glabrous intervals. Pronotal disc sculptured by coarse, or very coarse, transverse-wavy, or partly anastomosing ridges. Head temples moderately long, approximately 2 times shorter than eyes. Galea entirely black (or with slightly brownish apex of terminal galeomere). Labial palpi black, or partly or entirely testaceous. Antennae entirely black, or black-brown, or (in one species) predominantly ivory-testaceous. Legs with apical half of mesofemora, or also metafemora, more or less conspicuously subclavate-dilated, entirely black, except for one species with markedly bicoloured femora and tibiae. Aedeagus of various shapes.

Nomenclatorial note. Because of their regular elytral setal vesture, species of the subgenus Microgeniatum had been treated by Olsoufieff (1934), Jeannel (1946) and Horn (1934) in the nominotypical subgenus Pogonostoma. When Rivalier (1970) established the subgenus Microgeniatum for the three above-mentioned species, he included also Pogonostoma gladiator W. Horn, 1934 there. Due to extremely distinctive diagnostic characters of Pogonos- toma (Hornogeniatum) gladiator (unique within the whole genus), the species was placed later (Moravec 2007) into a separate, monobasic subgenus Hornogeniatum Moravec, 2007.

Distribution (Figs 11–14). Species of the subgenus are very rare, absent in most collections (including BMNH—see Moravec & Gillett 2009). Behaviour of adults is similar to most species of the silvicolous and strictly arboreal genus; developmental stages unknown. Somewhat more common is only P. (Microgeniatum) pseudomini- mum W. Horn, 1934 (type species of the subgenus), which is known from eastern Madagascar (Antongil Bay, dis- trict of Maroantsetra), penetrating through the forest of the Mananara Nord National Park (Province of Toamasina) to central area of Central Highlands, through Antsianaka near Lac Alaotra and the forest of Didy (both in the district of Ambatondrazaka) up to the forest of Analamazaotra-Perinet (type locality) east of Moramanga. The syntypes (1 ♂, 1 ♀, lectotype not designated) of P. (Microgeniatum) pseudominimum are deposited in SDEI; other specimens examined are in MNHN, CCJM, CJVB and JWCW (Moravec 2007 and recent personal data). The following two species have not been confirmed recently. P. (Microgeniatum) flavopalpale Jeannel, 1946 is known only from one male and one female (MNHN), caught in the forest of Piton Saint-Louis, north of Tolagnaro (= Fort Dauphin), 121 years ago. Only the male holotype (MNHN) of P. (Microgeniatum) infimum Rivalier, 1970 exists; it was caught in the deciduous forest of Analamerana, 50 km south-east of Antsiranana (= Diego Suarez) in northern Madagascar (in January 1959). Finally, P. (Microgeniatum) signifemorale sp. nov. is known only from the single male caught recently in the dense, dry deciduous forest of the Ankarafantsika National Park in northwestern Madagascar.