Stenichnus

Jałoszyński, Paweł, 2013, Revision of subgenera of Stenichnus Thomson, with review of Australo-Pacific species (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 3630 (1), pp. 39-79 : 41-50

publication ID	https://doi.org/ 10.11646/zootaxa.3630.1.2
publication LSID	lsid:zoobank.org:pub:A338EE37-E8AC-4AC3-8D6B-D0177FB680BF
DOI	https://doi.org/10.5281/zenodo.5696212
persistent identifier	https://treatment.plazi.org/id/03D687E5-B052-9A70-BDD1-413F122BF9BD
treatment provided by	Plazi
scientific name	Stenichnus
status	s. str.

Treatment

Morphology of Stenichnus View in CoL s. str.

General body shape ( Figs. 1–4 View FIGURES 1 – 4 ) elongate, body distinctly constricted between head and pronotum and pronotum and elytra, moderately to strongly convex; appendages long and moderately slender, vestiture moderately long and dense and composed of thin setae, without thick bristles.

Head capsule ( Figs. 5–8 View FIGURES 5 – 8 ) divided by occipital constriction ( Figs. 5, 7–8 View FIGURES 5 – 8 ; occ) into large anterior and small posterior part ('neck region'), the posterior part retracted into pronotum. Neck region ( Figs. 7–8 View FIGURES 5 – 8 ; nr) subcylindrical, broadest near middle and slightly narrowing towards foramen occipitale ( Figs. 7–8 View FIGURES 5 – 8 ; fo); narrowest site of occipital constriction only slightly narrower than vertex. Anterior part of head ( Figs. 5, 7–8 View FIGURES 5 – 8 ) approximately subtriangular, broadest at posteriorly located compound eyes ( Fig. 5 View FIGURES 5 – 8 ; ce) and narrowing anteriorly. Dorsum of head ( Fig. 5 View FIGURES 5 – 8 ) convex; tempora ( Figs. 5, 7 View FIGURES 5 – 8 ; tm) much shorter than eyes; vertex ( Fig. 5 View FIGURES 5 – 8 ; vt) transverse and nearly evenly convex, anteriorly confluent with subtrapezoidal and convex or flattened frons ( Fig. 5 View FIGURES 5 – 8 ; fr), which is gradually (not steeply) declining anteriorly; supraantennal tubercles feebly developed, often barely marked; genae ( Fig. 7 View FIGURES 5 – 8 ; gen) small. Clypeus ( Figs. 5–6 View FIGURES 5 – 8 ; cp) separated from frons but not from genae by distinct but short transverse fronto-clypeal groove ( Figs. 5–6 View FIGURES 5 – 8 ; fcg). Ventral side of head ( Fig. 8 View FIGURES 5 – 8 ) flattened except for strongly convex neck region; gular plate ( Figs. 6–8 View FIGURES 5 – 8 ; gp) subtrapezoidal, large, with rounded sides and distinct but fine gular sutures ( Figs. 6–8 View FIGURES 5 – 8 ; gs), distinctly demarcated from submentum ( Fig. 8 View FIGURES 5 – 8 ; smn) by deep groove; posterior tentorial pits located between gular plate and submentum, hidden in groove separating these structures.

Mouthparts ( Figs. 5–17 View FIGURES 5 – 8 View FIGURES 9 – 17 ). Labrum ( Figs. 5–6 View FIGURES 5 – 8 , 9, 11 View FIGURES 9 – 17 ; lb) transverse, with rounded sides slightly convergent anteriorly and nearly straight anterior margin with membranous marginal velum ( Fig. 9 View FIGURES 9 – 17 ; mv), dorsal surface with two transverse rows of four long setae in each. Epipharynx (ventral surface of labrum) ( Figs. 10, 12 View FIGURES 9 – 17 ; eph) with several anterior marginal seta-like sensilla ( Fig. 10 View FIGURES 9 – 17 ; ms), lateral groups of sparsely distributed trichia ( Fig. 10 View FIGURES 9 – 17 ; tr) directed antero-mesally and lateral groups of circular or oval glandular openings ( Fig 10 View FIGURES 9 – 17 ; gl). Mandibles ( Figs. 5, 8 View FIGURES 5 – 8 , 9, 11–13 View FIGURES 9 – 17 ; md) symmetrical, falciform, long and slender, with broadened base but without setose prostheca, with moderately deep basal pouch ( Figs. 9, 11 View FIGURES 9 – 17 ; bp) bearing two setae; basal part of mandible dorso-mesally with microsculpture composed of elongate cells ( Fig. 11 View FIGURES 9 – 17 ), distal part of mandible with finely denticulate mesal margin ( Fig. 13 View FIGURES 9 – 17 ). Maxillae ( Figs. 14, 16 View FIGURES 9 – 17 ) elongate, with large subtriangular cardo ( Fig. 16 View FIGURES 9 – 17 ; cd) bearing long sub-basal seta; basistipes ( Fig. 16 View FIGURES 9 – 17 ; bst) triangular, with one long basal and one long sub-basal lateral seta; mesostipes ( Fig. 16 View FIGURES 9 – 17 ; mst) elongate and broad, with three short median setae; palpifer ( Fig. 16 View FIGURES 9 – 17 ; ppf) elongate, with one long lateral sub-apical seta; galea ( Figs. 14, 16 View FIGURES 9 – 17 ; gal) elongate and slender, with long and dense trichia along distal margin and four long setae on external margin; lacinia ( Figs. 14, 16 View FIGURES 9 – 17 ; lac) elongate, with long and dense trichia along distal and mesal margins; maxillary palps ( Figs. 14–15 View FIGURES 9 – 17 ) long, palpomere I ( Fig. 14 View FIGURES 9 – 17 ; mxp1) small, as long as broad or only slightly longer and asetose, palpomere II ( Fig. 14 View FIGURES 9 – 17 ; mxp2) elongate and strongly thickening distally, with sparse setae, palpomere III ( Fig. 15 View FIGURES 9 – 17 ; mxp3) slightly longer than II and pedunculate, broadest near middle, nearly cylindrical in distal half, covered with sparse and long setae; palpomere IV ( Fig. 15 View FIGURES 9 – 17 ; mxp4) small, subconical, with elongate and pointed apical part, with dense and moderately long setae near base and asetose in distal third. Labium ( Figs. 8 View FIGURES 5 – 8 , 16–17 View FIGURES 9 – 17 ) with elongate, trapezoidal submentum ( Fig. 8 View FIGURES 5 – 8 ; smn) laterally separated from hypostomae ( Fig. 8 View FIGURES 5 – 8 ; h) by lateral sutures ( Fig. 8 View FIGURES 5 – 8 ; lss) and bearing a pair of long latero-anterior setae; mentum ( Figs. 8 View FIGURES 5 – 8 , 16 View FIGURES 9 – 17 ; mn) subtrapezoidal with one pair of long and one short latero-anterior setae; prementum ( Figs. 8 View FIGURES 5 – 8 , 16 View FIGURES 9 – 17 ; pmn) relatively long and flexible, with a pair of oval labial discs ( Fig. 17 View FIGURES 9 – 17 ; ld); labial palps slightly shorter than mentum, with broadly separated bases, palpomere I ( Figs. 16–17 View FIGURES 9 – 17 ; lp1) about as long as broad, asetose, palpomere II ( Figs. 16–17 View FIGURES 9 – 17 ; lp2) strongly elongate and slightly broadening distally, with two sub-median and sub-apical setae, palpomere III ( Figs. 16–17 View FIGURES 9 – 17 ; lp3) long and slender, asetose, with blunt apex. Hypopharynx (dorsal surface of labium) ( Fig. 14 View FIGURES 9 – 17 ; hph) with elongate lateral lobes ( Fig. 14 View FIGURES 9 – 17 ; llh) densely covered with microtrichia. Posteriorly and laterally mouthparts demarcated by hypostomal ridges ( Fig. 8 View FIGURES 5 – 8 ; hr) strongly convergent caudad; hypostomae ( Fig. 8 View FIGURES 5 – 8 ; h) subtriangular and elongate.

Antennae ( Figs. 1–4 View FIGURES 1 – 4 , 7 View FIGURES 5 – 8 ) slender, gradually thickening towards apices, antennomeres moderately compactly assembled, sparsely covered with suberect to erect setae.

Prothorax ( Figs. 18–21 View FIGURES 18 – 21 ) moderately convex, in dorsal view ( Fig. 18 View FIGURES 18 – 21 ) approximately pentagonal with rounded anterior part, without anterior corners, without lateral marginal carinae or sharp edges, posterior corners of pronotum blunt but well-defined. Pronotum ( Figs. 18, 20 View FIGURES 18 – 21 ; pn) with two pairs of small and shallow lateral ante-basal foveae ( Figs. 18–19 View FIGURES 18 – 21 ; bf), in some species foveae may be accompanied or replaced by a transverse row of small punctures. Prosternum ( Fig. 21 View FIGURES 18 – 21 ) about 3–4 times shorter than pronotum, with basisternal part ( Fig. 21 View FIGURES 18 – 21 ; bs) short and demarcated from procoxal cavities ( Fig. 21 View FIGURES 18 – 21 ; pcc) by distinct carina; procoxal cavities separated in middle by fine median prosternal intercoxal carina ( Fig. 21 View FIGURES 18 – 21 ; psc); procoxal sockets ( Fig. 21 View FIGURES 18 – 21 ; pcs) closed by lateral expansions of prosternum; profurcal foveae ( Fig. 21 View FIGURES 18 – 21 ; pff) relatively small. Hypomera ( Fig. 21 View FIGURES 18 – 21 ; hy) subtriangular, elongate, expanded mesally, not demarcated from pronotum, demarcated from sternum by notosternal sutures ( Fig. 21 View FIGURES 18 – 21 ; nss).

Mesothorax ( Figs. 22–30 View FIGURES 22 – 28 View FIGURES 29 – 31 ). Mesonotum ( Fig. 22 View FIGURES 22 – 28 ) subtriangular in shape; mesoscutum ( Fig. 22 View FIGURES 22 – 28 ; sc2) strongly transverse, with lateral groups of setae; scuto-scutellar suture ( Fig. 22 View FIGURES 22 – 28 ; sss) present and distinct; mesoscutellum ( Fig. 22 View FIGURES 22 – 28 ; scl2) well-visible between bases of elytra in intact specimens, subtriangular with concave sides and rounded posterior margin; anterior and posterior notal processes ( Fig. 22 View FIGURES 22 – 28 ; anp, pnp) prominent.

Mesoventrite ( Figs. 23–26 View FIGURES 22 – 28 , 29–30 View FIGURES 29 – 31 ) relatively short, much broader than long, with narrow anterior ridge ( Figs. 23, 26 View FIGURES 22 – 28 ; ar) bearing small subtriangular median projection not connected to mesoventral intercoxal process; mesoventrite behind anterior ridge with a pair of lateral asetose impressions ( Figs. 23, 26 View FIGURES 22 – 28 , 29 View FIGURES 29 – 31 ; ai) separated in middle and with large setose impressions ( Figs. 23, 26 View FIGURES 22 – 28 , 29 View FIGURES 29 – 31 ; si) narrowly separated in middle and narrowly separated from mesocoxal cavities; mesoventral intercoxal process ( Figs. 23, 26 View FIGURES 22 – 28 , 29–30 View FIGURES 29 – 31 ; msvp) narrow and moderately strongly projecting ventrally, posteriorly separated from metaventrite; mesocoxal cavities ( Figs. 23, 26 View FIGURES 22 – 28 , 29 View FIGURES 29 – 31 ; mscc) asetose, with anterior marginal carina ( Figs. 23–24 View FIGURES 22 – 28 ; amc), its lateral parts extending into mesocoxal projections ( Figs. 23 View FIGURES 22 – 28 , 29 View FIGURES 29 – 31 ; mcp), posterior margin of mesocoxal cavities with dense setae. Each mesocoxal projection with subtriangular posterior lobe ( Figs. 24–26 View FIGURES 22 – 28 ; pl) concealed by dense setae and best visible in transparent slide preparations; mesocoxal sockets ( Figs. 23, 26 View FIGURES 22 – 28 ; mscs) located laterally; mesofurcal foveae ( Figs. 23, 26 View FIGURES 22 – 28 ; msff) small and located sub-medially on lateral parts of mesocoxal cavities. Prepectus ( Figs. 23, 26 View FIGURES 22 – 28 , 29–30 View FIGURES 29 – 31 ; pre) very long and distinctly demarcated from mesocoxal projection and from posterior part of mesanepisternum ( Figs. 23 View FIGURES 22 – 28 , 29–30 View FIGURES 29 – 31 ; aest2), which is partly visible in ventral view and completely demarcated from mesepimeron; mesepimeron ( Fig. 30 View FIGURES 29 – 31 ; epm2) elongate and concave.

Metathorax ( Figs. 27–30 View FIGURES 22 – 28 View FIGURES 29 – 31 ). Premetascutum ( Figs. 27–28 View FIGURES 22 – 28 ; prsc3) large, transverse; metascutum ( Figs. 27–28 View FIGURES 22 – 28 ; sc3) very large and transverse, with robust oblique lateral apodemes ( Fig. 28 View FIGURES 22 – 28 ; ap) on ventral side, in middle with broad and impressed median membranous area ( Figs. 27–28 View FIGURES 22 – 28 ; mma); alacristae ( Figs. 27–28 View FIGURES 22 – 28 ; alc) nearly as long as scutum; metascutellum indiscernible, metascuto-scutellar suture indiscernible; metapostnotum ( Figs. 27–28 View FIGURES 22 – 28 ; psn3) large, strongly transverse.

Metaventrite ( Figs. 29–30 View FIGURES 29 – 31 ; v3) much longer than mesoventrite, broader than long, anteriorly fused with mesoventrite, with distinct metaventral anterior process ( Figs. 29–30 View FIGURES 29 – 31 ; mtap), lateral margins slightly rounded, lateral (admetacoxal) parts of posterior margin weakly concave, in middle posterior margin expanded caudad and forming broad and short subtrapezoidal metaventral intercoxal process ( Fig. 29 View FIGURES 29 – 31 ; mtvp) with distinct median notch. Metanepisternum ( Figs. 29–30 View FIGURES 29 – 31 ; aest3) partly visible in ventral view, strongly elongate and narrow, slightly narrowing caudad; metepimeron ( Fig. 30 View FIGURES 29 – 31 ; epm3) elongate, with dorsal sclerite distinctly broadening caudad.

Metafurca (metendosternite) ( Fig. 31 View FIGURES 29 – 31 ) with short stem ( Fig. 31 View FIGURES 29 – 31 ; mtfs) and strongly divergent lateral furcal arms ( Fig. 31 View FIGURES 29 – 31 ; mtfa) expanded at apices.

Elytra ( Figs. 1–4 View FIGURES 1 – 4 , 27 View FIGURES 22 – 28 ) oval, with rounded apices; humeri without denticle and with variously large, but distinct humeral callus; sub-humeral lines or carinae absent; elytral base with one moderately large, deep circular and asetose basal fovea ( Fig. 27 View FIGURES 22 – 28 ; bef) and visible only in transparent mounts trace of another fovea located close to humerus. Metathoracic wings (not shown) about twice as long as elytra, with posterior margin bearing dense fringe of long setae; venation highly reduced and homology of few indistinct veins visible only in basal part of wing difficult to interpret. Legs ( Figs. 1–4 View FIGURES 1 – 4 ) moderately long and slender, without special characters except for modifications in males of some species: profemora with angulate or rounded dorsal expansion, in some cases strongly flattened laterally; and (less frequently) metatibiae with a denticle or tooth-like projection.

Abdomen ( Figs. 32–33 View FIGURES 32 – 37 ) elongate, abdominal sternites III–VIII ( Fig. 32 View FIGURES 32 – 37 ; st3–8) gradually narrowing towards abdominal apex, sternite VIII longest; suture between sternite VII and VIII ( Fig. 32 View FIGURES 32 – 37 ) less distinct than between remaining sternites. Propygidium ( Fig. 33 View FIGURES 32 – 37 ; prpg) hidden under elytra, strongly sclerotized and densely covered with transverse rows of trichia; pygidium ( Fig. 33 View FIGURES 32 – 37 ; pg) exposed in intact specimens, strongly sclerotized, subtriangular with rounded apex, covered with setae.

Female terminalia ( Fig. 36 View FIGURES 32 – 37 ). Ovipositor lightly sclerotized and fragile; proctiger ( Fig. 36 View FIGURES 32 – 37 ; prc) subtriangular with rounded posterior margin, separated from fused and large paraprocts ( Fig. 36 View FIGURES 32 – 37 ; ppr); valvifers ( Fig. 36 View FIGURES 32 – 37 ; vf) elongate, distal margin of each with row of setae; coxites fused indistinguishably to valvifers; styli absent.

Spermatheca ( Fig. 37 View FIGURES 32 – 37 ) with distal globular and proximal tubular parts, insertion of accessory gland ( Fig. 37 View FIGURES 32 – 37 ; iag) located proximally on tubular part of spermatheca; ductus spermathecae ( Fig. 37 View FIGURES 32 – 37 ; ds) long and thin; spermatheca in intact specimens located deeply in abdomen or even inside metathorax.

Male terminalia ( Figs. 34–35 View FIGURES 32 – 37 ). Sternite IX ( Fig. 34 View FIGURES 32 – 37 ; st9) small and membranous; tergite IX ( Fig. 35 View FIGURES 32 – 37 ) composed of laterotergites connected by narrow median bridge, each with long lateral apodemes; tergite X ( Fig. 35 View FIGURES 32 – 37 ; t10) pentagonal with rounded apical margin.

Aedeagus ( Figs. 38–44 View FIGURES 38 – 44 ) bulbous, elongate but relatively stout, with rounded base of median lobe and moderately narrowing apically; ventral wall ( Figs. 38–39, 41–43 View FIGURES 38 – 44 ; vw) fused distally with ventral projection ( Figs. 38–39, 41–43 View FIGURES 38 – 44 ; vp) and laterally surrounded by narrow membranous area ( Figs. 38, 43 View FIGURES 38 – 44 ; ma); apical part of median lobe with strongly sclerotized meso-ventral and meso-dorsal projections ( Figs. 38–39, 41–43 View FIGURES 38 – 44 ; mvp, mdp) and elongate copulatory piece ( Figs. 41–42 View FIGURES 38 – 44 ; cp) protruding from between meso-dorsal projection and apical part of dorsal wall ( Figs. 41–42 View FIGURES 38 – 44 ; adw). Basal orifice ( Fig. 40 View FIGURES 38 – 44 ; bo) moderately large, located sub-basally on dorsal wall. Parameres ( Figs. 38–44 View FIGURES 38 – 44 ; pm) free (i.e., not fused with median lobe), slender, each with a group of apical setae ( Fig. 44 View FIGURES 38 – 44 ). Internal armature of aedeagus in transparent mounts ( Fig. 43 View FIGURES 38 – 44 ; ia) visible as darkly sclerotized internal parts of meso-ventral projection, meso-dorsal projection and copulatory piece, endophallus ( Fig. 43 View FIGURES 38 – 44 ; end) membranous, variously shaped, usually covered with fine denticles.

Remarks. Most of Palaearctic species of Stenichnus can be easily identified as belonging to this genus already on the basis of the general body shape and especially shapes of the head and pronotum, clearly different than in any other genus of Cyrtoscydmini that occurs in this large area. However, in other regions some genera may be highly similar to Stenichnus and it is necessary to examine the entire set of diagnostic characters to confirm determinations. Stenichnus seems to be most similar to Nearctic Brachycepsis Brendel, 1889 , a taxon previously treated as a subgenus of Stenichnus (elevated to a genus rank by Franz (1985)). Major differences between Stenichnus and Brachycepsis can be found in the shape of mandibles (falciform in Stenichnus vs. subtriangular with a small mesal tooth in Brachycepsis ); in the structure of prosternum (with fine intercoxal carina in Stenichnus vs. with a short, subtriangular intercoxal process in Brachycepsis ); in asetose impressions on the mesoventrite (separated in middle in Stenichnus vs. fused in middle in Brachycepsis ); and in the metaventral intercoxal process (short and broad in Stenichnus vs. long and narrow in Brachycepsis ). It remains to be studied whether Brachycepsis have the labial discs characteristic of Stenichnus ; this character is nearly impossible to notice in intact specimens in dry or transparent preparations, and a SEM study is required to analyze the structure of labium using specimens with the prementum exposed or on isolated mouthparts. For this reason, having only unique type specimens of most of the taxa treated below, with the labium in most cases concealed by maxillae and mandibles, in the present study the labial discs were not used to re-classify the subgenera of Stenichnus . The labial discs within Cyrtoscydmini may be in fact broadly distributed among genera that potentially share a common ancestor with Stenichnus . Other characters, both differences and similarities, are used to clarify the taxonomic status of taxa treated herein.