Amimoscydmus johnsoni (Franz) Jałoszyński, 2020

Jałoszyński, Paweł, 2020, Corrections to the classification of the Neotropical ant-like stone beetles misplaced in Euconnus Thomson (Coleoptera, Staphylinidae, Scydmaeninae). Part 1., Zootaxa 4755 (2), pp. 251-270 : 264-266

Amimoscydmus johnsoni (Franz) , comb. n.

Euconnus johnsoni Franz, 1880: 154 .

( Figs 30–39 )

Type material. Holotype: BRAZIL (Santa Catarina State): ♂, four historical labels ( Fig. 31 ): “BRAZIL vi/60 / Nova Teutonia / 300-500 m / F.Plaumann ” [white, handwritten and printed], “ Euconnus / johnsoni m. / det. H.Franz ” [white, handwritten and printed], “ Typus ” [red, handwritten], “Manchester Museum / HOLOTYPE ” [pink, printed]; during the present study a new label was added: “ AMIMOSCYDMUS / johnsoni ( Franz, 1980) / det. P. Jałoszyński, 2020” [white, printed] ( NHMW).

Diagnosis. BL> 0.90 mm; pronotum with lateral antebasal pits; mesoventrite with modified setae along posterior margins of procoxal rests; aedeagus in ventral view with abruptly narrowed, strongly elongated apical region.

Redescription. Body of male ( Fig. 30 ) relatively slender, moderately convex, brown, setae slightly lighter than cuticle; BL 0.95 mm.

Head ( Figs 32–33 ) broadest at large but weakly convex eyes, HL 0.13 mm, HW 0.18 mm; frons and vertex confluent, weakly convex, together about as long as broad, unmodified; supraantennal tubercles weakly marked; tempora slightly shorter than eye in dorsal view, distinctly bent mesad near posterior third. Vertex and frons with fine, inconspicuous punctures; setae short and suberect, sparse. Antennae ( Fig. 30 ) slender, AnL 0.38 mm; antennomeres I and II each elongate, III–X each transverse (VIII shorter than VII); XI distinctly shorter than IX and X combined, about 1.5 × as long as broad.

Pronotum ( Fig. 32 ) broadest slightly in front of middle; PL 0.23 mm, PW 0.23 mm. Anterior and posterior margins weakly arcuate; sides near middle strongly rounded, in posterior third indistinctly concave; pronotal base with two pairs of pits ( Fig. 32 ; abp), of which inner pair connected by sharply marked transverse groove ( Fig. 32 ; abg); sublateral carinae shifted laterad, so that appearing as short lateral carinae in posterior 1/4 of pronotal margin. Punctures on pronotal disc fine, inconspicuous; most setae on dorsal region of the only available specimen broken off, those on sides moderately long, sparse and erect.

Elytra ( Fig. 30 ) together oval, broadest distinctly in front of middle; EL 0.60 mm, EW 0.38 mm, EI 1.60; basal impressions short and shallow, basal foveae ( Fig. 32 ; bef) distinct (not vestigial); humeral calli distinct, elongate; elytral apices separately rounded. Punctures fine, inconspicuous; most setae broken off, few remaining are moderately long and suberect.

Hind wings long, functional.

Mesoventrite ( Figs 35–37 ) with conspicuously modified, broad and flat setae along posterior margins of procoxal rests ( Figs 35 , 37 ; ms).

Legs long and slender; unmodified.

Aedeagus ( Figs 38–39 ) elongate; AeL 0.20. Median lobe in ventral view drop-shaped, with rapidly narrowed, elongate subtriangular apical region; endophallus with paired elongate and recurved sclerites; parameres slender, each with one long apical seta.

Female. Unknown.

Distribution. Southern Brazil.

Remarks. This species cannot be included in Euconnus because of largely obliterated notosternal sutures (present and complete in Euconnus ), and the metaventral intercoxal process composed of a pair of long spines that do not separate metacoxae (metacoxae variously broadly separated by a process without spines in Euconnus ). Nearly all characters of the studied specimen agree with those of Amimoscydmus Jałoszyński, 2013 , except for the pronotum with lateral antebasal pits, which are absent in the type species of this genus. Only one species of Amimoscydmus was previously known, A. baruerii ( Franz, 1980) ; it occurs in Sao Paulo, Brazil ( Jałoszyński 2013). Amimoscydmus johnsoni has larger adults (0.95 mm, whereas the largest specimen of A. baruerii measures 0.63 mm), has the pronotal base with lateral pits (pits absent in A. baruerii ), and a clearly different aedeagus. The presence or absence of lateral antebasal pits is here added to the diagnosis of Amimoscydmus .

The holotype was indicated to be deposited at the Manchester Museum, The University of Manchester (Franz 1880), and it bars a label with this depository name. However, the specimen has never been returned, and is presently in NHMW.

Figures

FIGURES 30–32. Amimoscydmus johnsoni (Franz) comb. n., holotype male. Dorsal habitus (30); original set of labels (31); head, prothorax and elytral base in dorsal view (32). Abbreviations: abg, antebasal groove; abp, antebasal pit; bef, basal elytral fovea.

FIGURES 33–36. Amimoscydmus johnsoni (Franz) comb. n., holotype male. Head and prothorax in ventral view (33); prothorax in ventral view (34); mesothorax in ventral view (35); pterothorax in ventral view (36). Abbreviations: bst, basisternal part of prosternum; gp, gular plate; hr, hypostomal ridge; hyr, hypomeral ridge; mn, mentum; ms, modified setae; msvp, mesoventral intercoxal process; mtvp, metaventral intercoxal process; mxp1–4, maxillary palpomere I–IV; nss, notosternal suture; pcr, procoxal rest; smn, submentum.

FIGURES 37–39. Amimoscydmus johnsoni (Franz) comb. n., holotype male. Mesoventrite in ventral view (37); aedeagus in ventral (38) and lateral (39) views. Abbreviations: ms, modified setae; pcr, procoxal rest.