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

publication ID

http://dx.doi.org/10.11646/zootaxa.3794.2.2

publication LSID

lsid:zoobank.org:pub:E75F9E63-4785-49AB-AD6D-AC4838F39BAD

persistent identifier

http://treatment.plazi.org/id/03D3CE22-E373-5851-D4FB-300551062DA6

treatment provided by

Plazi

scientific name

Sciacharis
status

s. str.

subgenus Sciacharis  s. str.

Chathamaenus Franz, 1980 a: 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. 6–7View FIGURES 6 – 11) with occipital constriction ( Fig. 6View FIGURES 6 – 11; 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. 6View FIGURES 6 – 11; 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. 6View FIGURES 6 – 11; sat).

Labrum ( Fig. 6View FIGURES 6 – 11; lbr) transverse with rounded anterior margin. Mandibles ( Fig. 6View FIGURES 6 – 11; md) symmetrical, subtriangular, each with broad base and rapidly narrowing curved and pointed apex; prostheca present. Each maxilla ( Fig. 7View FIGURES 6 – 11) with subtriangular basistipes ( Fig. 7View FIGURES 6 – 11; bst), elongate galea ( Fig. 7View FIGURES 6 – 11; gal) and lacinia ( Fig. 7View FIGURES 6 – 11; lac) and strongly elongate and moderately large maxillary palp ( Fig. 7View FIGURES 6 – 11; 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. 7View FIGURES 6 – 11) with large submentum ( Fig. 7View FIGURES 6 – 11; smn) not demarcated posteriorly from gular plate and not demarcated laterally from postcardinal parts of hypostomae; subtrapezoidal mentum ( Fig. 7View FIGURES 6 – 11; mn); and short prementum ( Fig. 7View FIGURES 6 – 11; pmn) bearing narrowly separated at bases long 3 -segmented labial palps and a pair of median bristles. Hypostomal ridges ( Fig. 7View FIGURES 6 – 11; hr) long and extending nearly to posterior tentorial pits.

Gular plate ( Fig. 7View FIGURES 6 – 11; gp) large and subtrapezoidal, rapidly narrowing anteriorly; gular sutures ( Fig. 7View FIGURES 6 – 11; gs) superficial; posterior tentorial pits ( Fig. 7View FIGURES 6 – 11; ptp) narrow and arcuate, C-shaped.

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

Prothorax ( Figs. 12–13View FIGURES 12 – 17) 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. 12View FIGURES 12 – 17; mp) and shallow, elongate and small lateral pits ( Fig. 12View FIGURES 12 – 17; lp) adjacent to short sublateral carinae ( Fig. 12View FIGURES 12 – 17; slc) Sides of pronotum with dense, thick and long bristles ( Fig. 13View FIGURES 12 – 17).

Prosternum ( Fig. 13View FIGURES 12 – 17) with moderately short basisternal part ( Fig. 13View FIGURES 12 – 17; bst) indistinctly demarcated from procoxal cavities ( Fig. 13View FIGURES 12 – 17; pcc); median part of sternum slightly raised but not carinate; procoxal sockets ( Fig. 13View FIGURES 12 – 17; pcs) closed by narrow posterolateral lobes of prosternum, which are not fused to hypomera; hypomera ( Fig. 13View FIGURES 12 – 17; hy) elongate, each divided into broad lateral part confluent with pronotum and narrow internal (adcoxal) part; hypomeral ridges ( Fig. 13View FIGURES 12 – 17; hyr) complete; pronotosternal sutures ( Fig. 13View FIGURES 12 – 17; nss) entire.

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

Mesoventrite ( Fig. 18View FIGURES 18 – 21) with narrow and indistinctly demarcated anterior ridge ( Fig. 18View FIGURES 18 – 21; ar); mesoventral intercoxal process ( Fig. 18View FIGURES 18 – 21; 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. 18View FIGURES 18 – 21; si) distant from anterior margin of ventrite; mesanepisternum with moderately long prepectus ( Fig. 18View FIGURES 18 – 21; pre), with large, deep and setose ventrolateral fovea at each side ( Fig. 18View FIGURES 18 – 21; vlf); mesocoxal projections ( Fig. 18View FIGURES 18 – 21; mcp) prominent, with mesocoxal sockets located on their mesoventral surface and with exposed large posterior lobes ( Fig. 18View FIGURES 18 – 21; pl) bearing several bristles.

Metaventrite ( Fig. 18View FIGURES 18 – 21; v 3) subrectangular, anteriorly fused with mesoventrite, posteriorly moderately deeply bisinuate and with subtrapezoidal median metaventral intercoxal process ( Fig. 18View FIGURES 18 – 21; mtvp) not notched in middle. Metanepisterna and metepimera narrow.

Metafurca ( Fig. 18View FIGURES 18 – 21) with short stalk and divergent lateral furcal arms ( Fig. 18View FIGURES 18 – 21; 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. 22View FIGURES 22 – 24) 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 (1980 a) 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. 8–9View FIGURES 6 – 11), 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. 8View FIGURES 6 – 11; 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. 14View FIGURES 12 – 17) and a longer basisternal part of prosternum ( Fig. 15View FIGURES 12 – 17). Also the pterothorax ( Fig. 18View FIGURES 18 – 21 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 (1980 a). Therefore, the species, besides the remarkably modified head, can be identified also on the basis of the aedeagus ( Figs. 23–24View FIGURES 22 – 24), which is thin-walled and lightly sclerotized, with long parameres and a paired elongate structures in the internal sac.

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Coleoptera

Family

Staphylinidae

Loc

Sciacharis

Jałoszyński, Paweł 2014
2014
Loc

Chathamaenus

Franz 1980: 254