Sciacharis

Jałoszyński, Paweł, 2014, Comparative morphology and taxonomy of Sciacharis s. str., Chathamaenus Franz and Maorinus Franz (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 3794 (2), pp. 222-236 : 224-230

subgenus Sciacharis s. str.

Chathamaenus Franz, 1980a: 254 , syn. n.

Revised diagnosis. Head with anteriorly located eyes and long tempora, without frontoclypeal groove, with distinct 'neck region' and occipital constriction distinctly narrower than vertex; tempora and genae covered with thick bristles; submentum not demarcated from postcardinal parts of hypostomae (i.e., lateral sutures of submentum absent); hypostomal ridges nearly reaching elongate arcuate posterior tentorial pits; gular plate distinctly divided into broad posterior part located in 'neck region' and narrow anterior part; maxillary palpi slender; antennae gradually thickened distally; pronotum bell-shaped with two pairs of antebasal pits or impressions and short sublateral carinae; prosternum separated from hypomera by complete pronotosternal sutures; prothoracic hypomera with complete hypomeral ridges separating narrow internal (adcoxal) part of hypomera; procoxal sockets narrowly closed; prosternal process or carina absent; sides of pronotum covered with thick bristles; mesoventral intercoxal process carinate and not connected to anterior ridge of mesoventrite, interrupted near middle; mesoventrite with shallow setose impressions, without asetose impressions, and with one pair of deep ventrolateral foveae; metaventral intercoxal process without median notch; metacoxae contiguous; each elytron with two distinct and deep asetose basal foveae; aedeagus symmetrical, with free parameres (i.e., not fused to median lobe).

Redescription. Body (Fig. 1) moderately convex, elongate and slender, with moderately long appendages, pigmentation brown, cuticle setose.

Head ( Figs. 6–7 ) with occipital constriction ( Fig. 6 ; occ) distinctly narrower than vertex and dividing the head capsule into exposed anterior part and posterior 'neck region' retracted into prothorax; eyes located in anterior part of head; tempora ( Fig. 6 ; tm) long and with thick bristles; vertex broader than long, moderately convex, not projecting dorsocaudad; frons transverse and subtrapezoidal; frontoclypeal groove absent; antennal insertions broadly separated, located beneath distinct supraantennal tubercles ( Fig. 6 ; sat).

Labrum ( Fig. 6 ; lbr) transverse with rounded anterior margin. Mandibles ( Fig. 6 ; md) symmetrical, subtriangular, each with broad base and rapidly narrowing curved and pointed apex; prostheca present. Each maxilla ( Fig. 7 ) with subtriangular basistipes ( Fig. 7 ; bst), elongate galea ( Fig. 7 ; gal) and lacinia ( Fig. 7 ; lac) and strongly elongate and moderately large maxillary palp ( Fig. 7 ; mxp) composed of elongate palpomere I, strongly elongate, pedunculate and slender palpomere II, large and strongly elongate palpomere III broadest slightly distally to middle, and small, slender, subconical and pointed palpomere IV. Labium ( Fig. 7 ) with large submentum ( Fig. 7 ; smn) not demarcated posteriorly from gular plate and not demarcated laterally from postcardinal parts of hypostomae; subtrapezoidal mentum ( Fig. 7 ; mn); and short prementum ( Fig. 7 ; pmn) bearing narrowly separated at bases long 3-segmented labial palps and a pair of median bristles. Hypostomal ridges ( Fig. 7 ; hr) long and extending nearly to posterior tentorial pits.

Gular plate ( Fig. 7 ; gp) large and subtrapezoidal, rapidly narrowing anteriorly; gular sutures ( Fig. 7 ; gs) superficial; posterior tentorial pits ( Fig. 7 ; ptp) narrow and arcuate, C-shaped.

Antennae (Fig. 1) slender, gradually thickening distally.

Prothorax ( Figs. 12–13 ) in dorsal view bell-shaped, broadest anterior to middle, with rounded anterior margin and anterior parts of lateral margins, with weakly marked, blunt and obtuse anterior angles; sides in posterior third narrowed; posterior corners blunt and obtuse; posterior margin expanded posteriorly in middle. Pronotum with two pairs of pits: distinct, circular and large median pits ( Fig. 12 ; mp) and shallow, elongate and small lateral pits ( Fig. 12 ; lp) adjacent to short sublateral carinae ( Fig. 12 ; slc) Sides of pronotum with dense, thick and long bristles ( Fig. 13 ).

Prosternum ( Fig. 13 ) with moderately short basisternal part ( Fig. 13 ; bst) indistinctly demarcated from procoxal cavities ( Fig. 13 ; pcc); median part of sternum slightly raised but not carinate; procoxal sockets ( Fig. 13 ; pcs) closed by narrow posterolateral lobes of prosternum, which are not fused to hypomera; hypomera ( Fig. 13 ; hy) elongate, each divided into broad lateral part confluent with pronotum and narrow internal (adcoxal) part; hypomeral ridges ( Fig. 13 ; hyr) complete; pronotosternal sutures ( Fig. 13 ; nss) entire.

Mesoscutellum subtriangular, in intact specimen hidden by posterior margin of pronotum overlapping with elytral base.

Mesoventrite ( Fig. 18 ) with narrow and indistinctly demarcated anterior ridge ( Fig. 18 ; ar); mesoventral intercoxal process ( Fig. 18 ; msvp) carinate and moderately expanding ventrally, anteriorly separated from anterior ridge and interrupted near anterior margins of mesocoxal cavities; sides of mesoventrite without concave procoxal rests (= asetose impressions) but with large setose impressions ( Fig. 18 ; si) distant from anterior margin of ventrite; mesanepisternum with moderately long prepectus ( Fig. 18 ; pre), with large, deep and setose ventrolateral fovea at each side ( Fig. 18 ; vlf); mesocoxal projections ( Fig. 18 ; mcp) prominent, with mesocoxal sockets located on their mesoventral surface and with exposed large posterior lobes ( Fig. 18 ; pl) bearing several bristles.

Metaventrite ( Fig. 18 ; v3) subrectangular, anteriorly fused with mesoventrite, posteriorly moderately deeply bisinuate and with subtrapezoidal median metaventral intercoxal process ( Fig. 18 ; mtvp) not notched in middle. Metanepisterna and metepimera narrow.

Metafurca ( Fig. 18 ) with short stalk and divergent lateral furcal arms ( Fig. 18 ; lmfa).

Elytra (Fig. 1) oval, each with two small but distinct and deep asetose basal foveae; humeral calli distinct and developed as longitudinal protuberances; sub-humeral lines absent.

Hind wings well-developed, about twice as long as elytra.

Legs (Figs. 1, 13, 18) moderately long and slender; procoxae subglobose, mesocoxae oval, metacoxae strongly transverse; all trochanters short and unmodified; all femora weakly clavate; tibiae and tarsi long and slender.

Abdominal sternites in S. fulva partly damaged, but in other similar species of Sciacharis suture between VII and VIII distinct; sternites III–VI with bristles, and VII–VIII only with thin setae.

Aedeagus ( Fig. 22 ) of the holotype of S. fulva thin-walled and drop-shaped, broadest in basal part and narrowing toward broadly rounded apex that bears four narrow and pointed projections; internal armature lightly pigmented, indistinct; parameres long and slender, with apical setae. In other species internal armature is typically composed of large eversible internal sac covered with variously developed denticles or hair-like projections and symmetrical, also eversible sclerites.

Female. Unknown in S. fulva ; in other species sexual dimorphism weakly expressed; spermatheca globular, usually located deeply in metathorax.

Remarks. Discrimination between Euconnus and Sciacharis , common and abundant genera ( Euconnus cosmopolitan but Sciacharis mostly restricted to the southern hemisphere) is often difficult because of a highly similar dorsal habitus of many species. While sorting large museum collections, I have always had problems to separate these two genera, especially when specimens were mounted in such a way that the ventral characters could not be seen. It is relatively easy to distinguish Sciacharis s. str. from Euconnus s. str., the latter has the head without bristles on tempora (conspicuously long and dense bristles directed laterocaudad in Sciacharis s. str.), the pronotum broadest near base (anterior to middle in Sciacharis s. str.); short basisternal part of prosternum (long in Sciacharis s. str.), presence of dorsolateral foveae on mesoventrite (missing in Sciacharis s. str.), and broadly separated metacoxae (contiguous in Sciacharis s. str.) (morphology of Euconnus s. str. was described and illustrated in detail in Jałoszyński (2012)). Moreover, in all subgenera of Sciacharis species with sharply demarcated antennal club combined with subconical pronotum narrowing anteriorly from broad base (as in Euconnus ( Napochus Thomson, 1859 ) and several other subgenera of Euconnus ) are not known. However, the morphology of other subgenera of Euconnus has never been properly studied and it is possible that some of them will appear closer to Sciacharis than to Euconnus s. str. The morphology of Sciacharis s. str. and Euconnus s. str. is in fact highly similar, many important structures are shared by both taxa, suggesting their close relationships: the gular plate with rapidly narrowed anterior part; long hypostomal ridges; absent lateral sutures of submentum; absent prosternal process or carina; short internal (adcoxal) parts of prothoracic hypomera laterally demarcated by hypomeral ridges; narrowly closed procoxal sockets; bristles on the sides of prothorax; pronotal antebasal pits and carinae; structures of the mesoventrite including absence of asetose impressions and presence of deep ventrolateral foveae; and two asetose basal elytral pits. The diagnostic character used by Franz, the high mesoventral intercoxal process in Euconnus vs. low, rudimentary or absent process in Sciacharis , is of little value and in some cases it is difficult to assign a species to either genus on the basis of this sole structure.

The structures of Sciacharis s. str. are also highly similar to those of Horaeomorphus Schaufuss, 1889 , and some species of the former genus have been misplaced in the latter taxon (Jałoszyński, in preparation). However, as discussed in Jałoszyński (2012), a comprehensive reclassification of Cyrtoscydmini will be possible only when all previously established subgenera and genera have been revised and a phylogenetic analysis carried out. At the current state of knowledge it is important to record such numerous similarities and indicate differences that can be used to distinguish Sciacharis s. str. from Euconnus s. str. A comparative study of Sciacharis and Horaeomorphus will be a subject of a separate publication (Jałoszyński, in preparation). Further work is needed to clarify evolutionary relationships between all components of these complexes of genera.

The genus Chathamaenus was described by Franz (1980a) as most similar to Neuraphoconnus (i.e., to Sciacharis ( Magellanoconnus )), but differing from the latter in a number of characters, which have a rather low taxonomic value (e.g., the shape and setation of head) or were clearly misinterpreted (e.g., the base of pronotum in Chathamaenus bears not a groove, as stated by Franz, but pits). The general appearance of Ch. chathamensis (Figs. 2–3) is similar to that of S. fulva and other small and slender species of Sciacharis s. str. from Australia and adjacent islands. The striking character of Ch. chathamensis is the head ( Figs. 8–9 ), which is not flattened as in S. fulva , but strongly convex, with relatively small eyes partly concealed in dorsal view by expanded sides of the head. Also the posterior margin of vertex is not demarcated from occiput and the clypeus bears a large subtrapezoidal plate projecting dorsoanteriorly (clypeal projection; Fig. 8 ; clp). In all other characters the heads of S. fulva and Ch. chathamensis are similar and the differences can be ascribed to possible male secondary sexual characters in the latter species. A female, still unknown, would help clarifying this problem.

The prothoracic characters of S. fulva and Ch. chathamensis differ only in a more elongate pronotum ( Fig. 14 ) and a longer basisternal part of prosternum ( Fig. 15 ). Also the pterothorax ( Fig. 18 vs. 19–20) does not show any major differences, except for slightly narrower mesoventral intercoxal process with longer interruption in middle in Chathamaenus , which also lacks the posterior lobes of mesocoxal projections. These differences are too minor to justify a separate position of Chathamaenus and Sciacharis s. str, and these names are synonymized here.

Surprisingly, both type specimens of Ch. chathamensis are males, and not females, as stated by Franz (1980a). Therefore, the species, besides the remarkably modified head, can be identified also on the basis of the aedeagus ( Figs. 23–24 ), which is thin-walled and lightly sclerotized, with long parameres and a paired elongate structures in the internal sac.

Figures

FIGURES 6 – 11. Head capsule of males in dorsal (6, 8, 10) and ventral (7, 9, 11) views: Sciacharis (s. str.) fulva Broun (6 – 7); Sciacharis (s. str.) chathamensis (Franz), comb. n. (8 – 9); Sciacharis (Maorinus) sp. (10 – 11). Abbreviations: bst, basistipes; cd, cardo; clp, clypeal projection; fo, foramen occipitale; fr, frons; gal, galea; gp, gular plate; gs, gular suture; hr, hypostomal ridge; lac, lacinia; lbr, labrum; md, mandible; mn, mentum; mst, mediostipes; mxp, maxillary palpus; oc, occiput; occ, occipital constriction; pp, palpifer; prm, prementum; ptp, posterior tentorial pit; sat, supraantennal tubercle; smn, submentum; tm, temple; vt, vertex.

FIGURES 12 – 17. Prothorax in dorsal (12, 14, 16) and ventral (13, 15, 17) views: Sciacharis (s. str.) fulva Broun (12 – 13); Sciacharis (s. str.) chathamensis (Franz), comb. n. (14 – 15); Sciacharis (Maorinus) sp. (16 – 17). Abbreviations: bst, basisternal part of prosternum; hy, hypomeron; hyr, hypomeral ridge; lp, lateral antebasal pit; mp, median antebasal pit; nss, pronotosternal suture; pcc, procoxal cavity; pcs, procoxal socket; pf, profurca; slc, sublateral carina.

FIGURES 18 – 21. Pterothorax in ventral view: Sciacharis (s. str.) fulva Broun (18); Sciacharis (s. str.) chathamensis (Franz), comb. n. with (19) and without (20) setation; Sciacharis (Maorinus) sp. (21). Abbreviations: ar, anterior ridge; lmfa, lateral mesofurcal arm; mcp, mesocoxal projection; mff, mesofurcal fovea; mscc, mesocoxal cavity; msvp, mesoventral intercoxal process; mtvp, metaventral intercoxal process; pl, posterior lobe; pre, prepectus; si, setose impression; v 3, metaventrite; vlf, ventrolateral foveae.

FIGURES 22 – 24. Aedeagus of holotypes in ventral (22 – 23) and lateral (23) views: Sciacharis (s. str.) fulva Broun (22); Sciacharis (s. str.) chathamensis (Franz), comb. n. (23 – 24).