Perumicrus, Jałoszyński, Paweł, 2015

Jałoszyński, Paweł, 2015, Revision of Neotropical species of ant-like stone beetles misplaced in Stenichnus and Scydmoraphes (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 4027 (2), pp. 253-269 : 264-267

Perumicrus gen. nov.

Type species: Scydmoraphes peruanus Franz, 1980a: 210 (here designated).

Diagnosis. The unique apomorphy of this genus is the structure of prothoracic hypomeron and lateral portion of prosternum: the notosternal suture is marked only near anterior prosternal margin and near procoxal socket, its median part is externally not visible, posterior (adcoxal) part of notosternal suture anteriorly connects with additional suture extending posterolaterally and joining hypomeral ridge, thus demarcating inner part of hypomeron from prosternum, postcoxal area of inner part of hypomeron is fused with prosternum, and hypomeral ridge in front of procoxa runs laterally to notosternal suture. Additional diagnostic characters comprise: head transverse and with tempora much shorter than eyes and without bristles, occipital constriction distinctly narrower than vertex but not narrower than frons between eyes; antenna with club composed of antennomeres IX–XI; pronotum without lateral edges, with antebasal transverse groove and one pair of lateral impressions separated from groove; sides of pronotum lacking bristles; prosternum with basisternal part slightly shorter than coxal part; prosternal process absent; mesoventral intercoxal process long, carinate but moderately elevated, extending from anterior ridge of mesoventrite to posterior margins of mesocoxae; mesothorax lacking lateral foveae; metaventral intercoxal process very narrowly separating metacoxae, with two long spines; each elytron with one small but distinct asetose basal fovea; and symmetrical aedeagus with slender parameres.

Description. Body of male moderately strongly convex, slender, with moderately long appendages, BL below 1 mm; cuticle glossy, brown, moderately densely setose.

Head ( Figs 21–22 ) short and approximately subtrapezoidal, with very large eyes; occipital constriction ( Fig. 21 ; occ) in the narrowest place slightly broader than frons; 'neck' region ( Fig. 21 ; nr) much broader than long, slightly narrower than vertex; tempora shorter than eyes and strongly convergent posteromesally; vertex ( Fig. 21 ; vt) strongly transverse; frons ( Fig. 21 ; fr) posteriorly confluent with vertex, subtrapezoidal, anteriorly slightly projecting at middle; frontoclypeal groove absent; antennal insertions moderately broadly separated. Tempora and posterior margin of vertex lacking bristles.

Labrum transverse with rounded anterior margin. Each mandible subtriangular, mesal margin not visible in the studied specimen. Each maxilla with short and broad cardo ( Fig. 22 ; cd), subtriangular basistipes ( Fig. 22 ; bst), short mediostipes ( Fig. 22 ; mst) and elongate galea ( Fig. 22 ; gal) and lacinia ( Fig. 22 ; lac), each with dense setae along distomesal margin, maxillary palp ( Fig. 22 ; mxp) moderately long, palpomere I minute, slightly longer than broad, palpomere II strongly elongate, nearly pipe-shaped, palpomere III relatively stout, broadest between middle and distal third, palpomere IV very slender, nearly rod-like. Labium with broad submentum ( Fig. 22 ; smn) not demarcated laterally by sutures; subtrapezoidal mentum ( Fig. 22 ; mn) and short prementum, ligula indistinct; labial palps ( Fig. 22 ; lp) short, moderately broadly separated at bases, with palpomere II relatively long. Hypostomal ridges ( Fig. 22 ; hy) distinct but posteriorly not reaching posterior tentorial pits.

Gular plate ( Fig. 22 ; gp) broadly subtrapezoidal with rounded sides, gular sutures ( Fig. 22 ; gs) superficial. Posterior tentorial pits ( Fig. 22 ; ptp) exposed, arcuate, located in transverse impression demarcating 'neck' region.

Antennae ( Fig. 21 ) with club composed of antennomeres IX–XI.

Pronotum in dorsal view subquadrate with rounded sides, anterior margin nearly straight, anterior corners distinct, obtuse-angled, sides rounded in anterior half and distinctly narrowing posteriorly, posterior corners distinct, slightly obtuse-angled, posterior margin shallowly bisinuate. Pronotum without lateral edges, with distinct antebasal transverse groove and one pair of longitudinally elongate lateral impressions close to lateral margins and not connected with groove. Sides of pronotum lacking bristles.

Prosternum ( Fig. 23 ) with basisternal part ( Fig. 23 ; bst) indistinctly demarcated from coxal part and only slightly shorter than the latter; intercoxal area slightly elevated but diffused, not forming prosternal process; procoxal sockets ( Fig. 23 ; pcs) broadly closed. Notosternal sutures ( Fig. 23 ; nss) incomplete, externally visible only at anterior prosternal margin and in front of procoxal socket while median part is obliterated, adcoxal part of notosternal suture connected to oblique suture extending posterolaterally and connecting to hypomeral ridge. Hypomeral ridge ( Fig. 23 ; hyr) nearly complete, its precoxal part running laterally to notosternal suture. Inner part of hypomeron fused with postcoxal part of prosternum.

Mesoscutellum in studied specimens not visible.

Mesoventrite ( Fig. 24 ) with narrow anterior ridge ( Fig. 24 ; ar) and long, carinate mesoventral intercoxal process ( Fig. 24 ; msvp) which is moderately elevated (in lateral view not projecting ventrally beyond ventral margins of mesocoxae) and extending from anterior ridge to posterior margins of mesocoxae. Mesothorax lacking lateral foveae. Mesocoxal projections ( Fig. 24 ; mcp) prominent, with mesocoxal sockets ( Fig. 24 ; mscs) located on their mesoventral surface and exposed in ventral view. Mesoventrite with large asetose procoxal rests ( Fig. 24 ; pcr); area behind procoxal rests asetose and not impressed.

Metaventrite ( Fig. 24 ; v3) subtrapezoidal, broadening posteriorly and with rounded sides; metaventral intercoxal process ( Fig. 24 ; mtvp) very narrowly separating metacoxae and with two long spines. Metanepisterna and metepimera narrow. Lateral margins of metacoxae distant from lateral margins of metaventrite. Metendosternite (metafurca) with very short stem and divergent lateral furcal arms ( Fig. 24 ; lmfa).

Elytra oval, each with one small but distinct asetose basal fovea.

Legs moderately long and slender; pro- and mesocoxae oval, metacoxae transverse; all femora weakly and gradually clavate, all tibiae slender and nearly straight; tarsi moderately slender.

Abdominal sternites unmodified, suture between two terminal sternites distinct.

Aedeagus ( Figs 11 , 27 ) drop-shaped, elongate, with both median lobe and endophallus symmetrical; median lobe with subtriangular apical part; endophallus composed of paired elongate sclerites; parameres present, slender and with apical setae.

Distribution and composition. One species of Perumicrus is known to occur in Peru.

Etymology. The name Perumicrus is composed of the country name and - micrus, referring to the small body of the type species. Gender masculine.

Remarks. The following characters clearly indicate that Scydmoraphes peruanus is not congeneric with Northern Hemisphere Scydmoraphes : submentum lacking lateral sutures (present in Scydmoraphes ); posterior tentorial pits exposed (hidden in deep transverse groove demarcating 'neck region' in Scydmoraphes ); anterior margins of eyes nearly adjacent to mandibular bases (distant in Scydmoraphes ); antennae with distinct club composed of three terminal antennomeres (gradually thickened in Scydmoraphes ); maxillary palpomere IV very slender, nearly rod-like (subconical with broad base in Scydmoraphes ); sides of pronotum without bristles (present in Scydmoraphes ); prosternum in front of and behind procoxal sockets laterally broadly fused with inner parts of hypomera (not fused in Scydmoraphes ); notosternal sutures largely internalized and visible only near anterior margin of prosternum and near procoxal socket (complete in Scydmoraphes ); mesoventral intercoxal process extending from anterior ridge of mesoventrite to posterior margins of mesocoxae (posteriorly reaching only middle of mesocoxae in Scydmoraphes ); anterior metaventral process absent (present in Scydmoraphes ); and metaventral intercoxal process with pair of long spines (lacking spines in Scydmoraphes ).

Scydmoraphes peruanus shows characters resembling similarly minute species of genera Mimoscydmus Franz, 1980a , Amimoscydmus Jałoszyński, 2013b and Microraphes Franz, 1980a . However, the structure of prosternum in Scydmoraphes peruanus is unique and represents an autapomorphy to define a new genus, Perumicrus : the notosternal suture is marked only as a short notch in anterior margin of sternum and posteriorly as a short suture running anterad from procoxal socket, the median part is internalized and externally not visible, posterior part of notosternal suture connects to an additional oblique suture extending laterocaudad to join hypomeral ridge, and these two sutures demarcate the inner (adcoxal) part of hypomeron from prosternum, while posteriorly (behind coxal socket) this part of hypomeron is fused with postcoxal part of prosternum. Moreover, the hypomeral ridge runs laterally to notosternal suture and not, as in most Cyrtoscydmini , connects with the suture or overlaps it in precoxal region. This relatively complex modification is not known in any other genus, although various extent of fusion of prosternum with hypomeron can be seen in some genera, especially those characterized by very small body size. The probably plesiomorphic character state in Cyrtoscydmini is a complete notosternal suture and inner part of hypomeron entirely demarcated from prosternum, with hypomeral ridge anteriorly confluent with, joining or overlapping notosternal suture.

As mentioned in the previous paragraph, Perumicrus shows characters similar to those of Mimoscydmus, Amimoscydmus and Microraphes . Additionally to already listed characters, it differs from Mimoscydmus in the pronotum without lateral bristles (bristles present in Mimoscydmus ), presence of lateral pronotal antebasal impressions (lacking in Mimoscydmus ), prosternal intercoxal area lacking prosternal process (carinate process in Mimoscydmus ), and lack of ventrolateral mesothoracic foveae (present in Mimoscydmus ). Perumicrus differs from Amimoscydmus Jałoszyński in hypostomal ridges posteriorly reaching nearly to tentorial pits (ridges very short, visible only just behind cardines in Amimoscydmus), presence of lateral pronotal antebasal impressions (lacking in Amimoscydmus), prosternal intercoxal region lacking prosternal process (narrow carinate process present in Amimoscydmus), inner (adcoxal) part of hypomeron in front of procoxal socket demarcated by prosternum by rudiment of notosternal suture connected anteriorly to oblique suture that posteriorly connects with hypomeral ridge (inner part of hypomeron in front of procoxal socket fused with prosternum in Amimoscydmus); and each elytron with one distinct basal fovea (two rudimentary foveae in Amimoscydmus). Perumicrus differs from Microraphes Franz in hypostomal ridges posteriorly reaching nearly tentorial pits (ridges very short, visible only just behind cardines in Microraphes ), sides of pronotum without bristles (dense thick bristles in Microraphes ), presence of lateral pronotal antebasal impressions (lacking in Microraphes ), prosternum much broader than long, with basisternal part indistinctly demarcated from coxal part (prosternum subquadrate in Microraphes and basisternal part demarcated by carina), inner (adcoxal) part of hypomeron in precoxal region demarcated, and in postcoxal region fused with prosternum (in Microraphes fused in precoxal region while demarcated in postcoxal region), prosternal intercoxal process missing (short but distinct in Microraphes ), and metaventral intercoxal process with two long spines (lacking in Microraphes ).

Figures

FIGURES 21 – 24. Morphological structures of Perumicrus peruanus (Franz), paratype male. Head in dorsal (21) and ventral (22) views; prothorax in ventral view (23); pterothorax in ventral view (24). Abbreviations: ar, anterior ridge of mesoventrite; bst, basisternal part of prosternum; bst, basistipes; cd, cardo; fr, frons; gal, galea; gp, gular plate; gs, gular suture; h, hypomeron; hy, hypostomal ridge; hyr, hypomeral ridge; lac, lacinia; lb, labrum; lp, labial palp; lmfa, lateral metafurcal arm; mcp, mesocoxal projection; md, mandible; mn, mentum; mscc, mesocoxal cavity; mscs, mesocoxal socket; msff, mesofurcal fovea; mst, mediostipes; msvp, mesoventral intercoxal process; mtvp, metaventral intercoxal process; mxp, maxillary palp; nr, ' neck' region; occ, occipital constriction; pf, profurca; pre, prepectus; pcc, procoxal cavity; pcs, procoxal socket; ptp, posterior tentorial pits; smn, submentum; v 3, metaventrite; vlf, ventrolateral fovea; vt, vertex.

FIGURES 9 – 11. Meridaphes venezolanus (Franz) (9, 10) and Perumicrus peruanus (Franz) (11). Dorsal habitus of male holotype (9) and aedeagus in ventral view (10, 11).

FIGURES 25 – 27. Meridaphes venezolanus (Franz) (25, 26) and Perumicrus peruanus (Franz) (27). Aedeagus in ventral (25, 27) and lateral (26) views.