Antimerus Fauvel 1878

Solodovnikov, A. & Newton, A. F., 2010, Revision of the rove beetle genus Antimerus (Coleoptera, Staphylinidae, Staphylininae), a puzzling endemic Australian lineage of the tribe Staphylinini, ZooKeys 67, pp. 21-63 : 24-28

Genus Antimerus Fauvel 1878

Antimerus Fauvel 1878: 550.

Type species:

Antimerus smaragdinus Fauvel, 1878 (by monotypy).

Diagnostic description.

(Figs 1-18, 21-42). Large Staphylinini (13-20 mm extended), robust, more or less parallel-sided with head about as wide as pronotum, elytra and abdomen (Figs 9-18).

Head transverse; neck about half as wide as head, distinct at sides but not or indistinctly marked dorsally; eye large, occupying more than half of side of head; temple short, hind angle of head broadly rounded or indistinct; antenna slender, longer than head width, increasingly densely pubescent from about antennomere 6 to apex; labrum (Fig. 1) very short and wide, about 2/3 as wide as head, with sclerotized anterior margin and acute median emargination; mandible (Fig. 3) long, slender, falcate, about as long as head excluding neck, with narrow bladelike medial edge along apical half or more, edentate or at most with one small tooth along medial edge of basal half, with short abruptly expanded base, and without prostheca (except Antimerus auricomus with very slender prostheca no longer than width of mandible at base); maxillary (Fig. 4) and labial (Fig. 2) palps with robust, elongate apical palpomeres that are about as wide or wider than more basal palpomeres and with abruptly truncate apices; galea and lacinia densely setose; paraglossa very long, fingerlike, with comb of strong setae along mesial edge; glossae short, densely setose; prementum small, transverse; mentum transverse, broadly emarginate at apex; gular sutures (Fig. 6) complete, closely approximate through much of length; postgenal (Fig. 6, pg) and ventral basal (Fig. 6, vb) ridges well-developed, nuchal ridge absent, infraorbital ridge (Fig. 6, io) rudimental, short.

Pronotum (Fig. 5) subquadrate to strongly transverse; superior line of hypomeron continued onto anterior margin, visible from above (except in Antimerus posttibialis where it is deflexed ventrad and not visible from above in apical fourth); inferior line of hypomeron complete except interrupted at coxal articulation, or more or less obsolete; hypomeron with large triangular partly translucent post-coxal process; hypomeron completely visible from side (except in Antimerus monteithi sp. n. where it is inflexed and completely hidden in lateral view except for apex of postcoxal process); notosternal suture (Fig. 5, ns) complete, distinct; prosternum short, transverse, its anterior edge laterally not forming an abrupt angle with hypomeron; procoxal cavities largely closed behind by very large mesothoracic spiracles (Fig. 5, spi) plus a smaller irregular median sclerotized area (Fig. 5, msa) between the spiracles.

Scutellum large, triangular, with two transverse subbasal carinae. Elytron without epipleural ridge; elytra together about as long as wide. Hind wings fully developed and functional, each with completely separate MP4 and CuA veins. Mesocoxae contiguous, mesocoxal cavities delimited anteriorly and posteriorly by carinae (Fig. 7). All tarsi 5-segmented, tarsomeres 1-4 of all legs of both sexes more or less broad, basal tarsomeres of front legs as wide as or wider than width of protibia, those of other segments narrower than width of corresponding tibiae; tarsomeres 1-4 of all legs with dense brushes of tenent setae ventrally; tarsal claws simple, empodium with pair of setae that are shorter than claws.

Abdomen without prototergal gland (Fig. 8), apparently without eversible defensive glands posterior to tergum VIII. Tergites II–VIII and sternites III–VIII each with a single subbasal carina that is curved posteriad at sides (behind spiracle on tergites); tergites III–VIII also with short oblique anterolateral carina before spiracle. Segments III–VII with two pairs of laterotergites each, the dorsal laterotergites on III–VI each with a subbasal carina. Intersegmental membranes between segments III–VII attached preapically to preceding segment, with irregular or quadrangular, more or less rounded sclerites occupying less than 70% of membrane surface. Sternum VIII with slight to moderate apical emargination in male, with no or more shallow emargination in female; sexual dimorphism otherwise restricted to genital segment and associated genitalia.

Genital segment of both sexes with triangular tergum X which widely separates lateral tergites IX dorsally, and each lateral tergite IX produced into hollow, fingerlike, apically obtuse or rounded process. Male sternite IX entire, more or less symmetrical or with base slightly more produced anteriad on left side (Fig. 7a). Aedeagus (Figs 21-42) with parameres fused into a single large apically emarginate lobe which bears dense field of dark peg setae facing median lobe, and at least 4 pairs of apical setae; median lobe elongate, tubular for most of length with basal membranous area bearing pair of flaps, apex more or less triangularly produced to extend slightly beyond apex of paramere; internal sac with large well sclerotized copulatory sclerite that abuts apex of median lobe when internal sac everted, and pair of more distal membranous or partly sclerotized lobes; aedeagus in repose in abdomen with paramere facing left side of beetle. Female without median ventral sclerite, ovipositor consisting of paired proximal and distal gonocoxites, styli apparently absent; spermatheca apparently not sclerotized.

Distribution and bionomics.

(Figs 55, 56) All hitherto known species of Antimerus (see below) are confined to the moist forests of the coastal hills and mountain ranges of eastern Australia, from northern Queensland to Victoria, South Australia and Tasmania. However, there is a significant gap in this arc: the genus is not known to occur for a long stretch in central and southern Queensland (Fig. 55, A–C). This seems to be not a sampling artifact, but a real disjunction coinciding with the gap in the distribution of moist forests in eastern Australia ( Groves 1994). Apart from evidence that species of Antimerus are apparently confined to forests (e.g., Fig. 56), very little is known about their microhabitat preferences, which seem to vary from one species to another (see species details below). Available label data, our own collecting experience, and morphology of the genus (large eyes, expanded tarsi of all legs) suggest that at least some species of the genus are diurnal and more or less arboreal. Arboreality may explain their rarity in collections, which have been mostly obtained by methods targeting microhabitats on or near the ground.

Comparison.

In Australia, Antimerus can be distinguished from any other genus of the tribe Staphylinini by the following combination of characters: relatively large body size (13-20 mm); relatively long falcate mandibles without distinct teeth internally (except small tooth on left mandible only in two species); deflexed hypomera of pronotum visible in lateral view (except Antimerus monteithi , concealed); tarsomeres 1-4 of all legs in both sexes broad and bearing tenent setae ventrally; and one pair of empodial setae on all tarsi. The only sympatric genus likely to be confused with Antimerus is Lonia which has distinct mandibular teeth internally and simple meso- and metatarsi (Fig. 20).

Key to Antimerus species (adults)

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