Clidicus Laporte, 1832

Paweł Jałoszyński, 2018, World genera of Mastigitae: review of morphological structures and new ecological data (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 4453 (1), pp. 1-119 : 40-49

Clidicus Laporte

Clidicus Laporte de Castelnau, 1832 : 396. Type species: Clidicus grandis Laporte de Castelnau, 1832 (monotypy).

Erineus Walker, 1858: 205 . Type species: Erineus monstrosus Walker, 1858 (monotypy). Synonymized with Clidicus by Pascoe, 1863.

Diagnosis. Differs from other Clidicini in vertex lacking a pair of long bristles; labial palpomere II barrel-shaped, weakly broadened distad; and labial palpomere IV rod-like, slender but not bristle-like.

Characteristic. Adult. Body ( Figs 78–83 ) small to large, in extant species 2.99̄8.50 mm in length, in extinct species 3.55–4.08 mm (nominal species) to ~ 6 mm (undescribed Baltic amber species), light to dark reddish brown, one species red with dark brown head; strongly convex, dorsally densely setose, setae long and suberect to

erect, unmodified except for variously developed longer and more erect bristles distributed on antennae, maxillary palps, head capsule and legs.

Head capsule ( Figs 84–85 , 90–91 ) divided into large and exposed anterior part and much smaller, subcylindrical 'neck' region retracted into prothorax and demarcated by distinct occipital constriction; 'neck' region about as broad as half width of head. Anterior part of head strongly flattened, typically subequal in width with prothorax, transverse or (rarely) about as long as broad, broadest behind middle or (rarely) at middle. Composite eyes dorsolateral, near anterior margin of head, small but composed of numerous small ommatidia, weakly convex. Vertex strongly transverse and posteriorly impressed at middle, convex at sides, with posterior margin concave. Tempora long and rounded. Frons between antennal insertions broadly subtrapezoidal, anteriorly demarcated by a deep and complete frontoclypeal groove ( Fig. 90 ; fcg). Clypeus very short and broad, with rounded or straight sides. Antennal insertions ( Fig. 90 ; ai) located anterodorsally, broadly separated. Gular plate ( Fig. 91 ; gp) lacking sutures, nearly smooth; posterior tentorial pits ( Fig. 91 ; ptp) arcuate, in front of transverse impression demarcating 'neck' region ventrally; hypostomal ridges ( Fig. 91 ; hr) nearly straight or arcuate, posteriorly nearly reaching posterior tentorial pits. Head with or without punctures, densely setose, often with conspicuously long setae ( Fig. 84 ).

Antennae ( Figs 78–85 , 95 ) shorter or about as long as body, slender; scape ( Fig. 95 ; sc) 4̄6 times as long as broad, usually slightly broadening distad, with very deep lateroventral emargination; pedicel ( Fig. 95 ; pd) typically shorter than, less frequently about as long as antennomere III and broadening from narrow base to apex; antennomeres III–X elongate (usually strongly, less frequently weakly) and weakly thickening distally, basal stalks not exposed, basal rings absent or indistinct; antennomere XI elongate and slightly asymmetrical. Antennomeres covered with variously dense, long setae; surface of antennomeres smooth in most specimens.

Mouthparts. Labrum ( Fig. 92 ; lbr) strongly transverse, variable in shape, with lateral margins parallel or (more frequently) divergent anterad, nearly straight or rounded, and with anterior margin straight, concave, emarginated or notched at middle, or with a row of variously shaped anterior teeth or denticles, with a transverse dorsoanterior row of long setae. Mandibles ( Figs 90–92 ) symmetrical, subtriangular and robust, with at least three (typically five) preapical teeth of various lengths, forming two groups, which are ventral and dorsal in relation to slender mandibular apex and the coronal plane of mandible; setose prostheca present and occupying more than basal half of mandible. Maxilla ( Fig. 94 ) with large but relatively short cardo ( Fig. 94 ; cd); basistipes ( Fig. 94 ; bst) subtriangular and elongate; mediostipes ( Fig. 94 ; mst) large and sharply demarcated from lacinia ( Fig. 94 ; lac) and galea ( Fig. 94 ; gal), which are both elongate and curved mesally and each with dense row of distal setae; palpifer ( Fig. 94 ; ppf) broad and elongate; maxillary palp ( Figs 84–85 , 93–94 ) composed of minute palpomere I, elongate and broadening distally palpomere II, palpomere III ( Fig. 93 ; mxp3) subtriangular, broadening distad, with oblique distal margin, palpomere IV ( Fig. 93 ; mxp4) subtriangular, with pointed apex, its base typically narrower than apical width of palpomere III or subequal; palpomeres III and IV subcylindrical or variously distinctly flattened. All palpomeres densely covered with variously long setae, palpomere II and/or III with some long and more erect setae among suberect and shorter basic vestiture ( Fig. 84 , in some species indistinct). Labium ( Figs 91–94 ) with broad submentum ( Fig. 91 ; smn) posteriorly not demarcated from gular region, bearing a pair of long thin setae near its anterior margin or in subanterior region; mentum ( Fig. 94 ; mn) subtrapezoidal and strongly transverse, with anterior margin straight or broadly rounded; prementum ( Fig. 94 ; pm) long, subtrapezoidal, broadest distally, lacking demarcated ligula, with a pair of anterolateral setae, with broadly separated bases of labial palps; lateral hypopharyngeal lobes ( Fig. 94 ; lhl) moderately large; labial palp ( Fig. 91 ; lp) composed of three palpomeres: palpomere I ( Fig. 94 ; lp1) small, elongate, broadening distad, palpomere II ( Fig. 94 ; lp2) largest, strongly elongate and only indistinctly broadening distad, palpomere III ( Fig. 94 ; lp3) narrow, long and pointed.

Prothorax ( Figs 78–85 , 96 ) about as long as broad or weakly elongate, strongly convex, broadest near anterior third. Pronotum with anterior and posterior margins arcuate or nearly straight, sides rounded in anterior half and usually sinuate in posterior half; anterior corners broadly rounded, posterior corners obtuse-angled; pronotal base with a short posterior 'collar' demarcated by a dorsal transverse row of several variously distinct pits, nearly always connected by a groove. Prosternum ( Fig. 96 ) with basisternal part ( Fig. 96 ; bstr) subequal in length to coxal part, but proportions depend on the shape of pronotum, in species with short pronota basisternal part tends to be indistinctly shorter than coxal part, in species with elongate pronota basisternal part can be longer than coxal part. Prosternum laterally completely fused with hypomera. Coxal region demarcated anteriorly by carina extending laterally up to apices of very weakly developed adcoxal hypomeral lobes. Procoxal cavities broadly open. Prosternal intercoxal process indistinct, usually developed as a diffuse and weakly elevated ridge hidden between procoxae. Ventral surface of prothorax typically densely setose, in some species with particularly dense and long erect setae on anteroventral portions of hypomera ( Fig. 84 ).

Mesoventrite ( Figs 84–85 , 97 ) subtrapezoidal, broadening posteriorly. Prepecti ( Fig. 97 ; pre) long and together with anteromedian mesoventral area forming a massive 'collar', which bears a transverse groove just behind its anterior ridge ( Fig. 97 ; ar), its posterior margin bisinuate with short subtriangular or subtrapezoidal posteromedian projection, which is broadly separated from a similar anteromedian projection of posterior margin of setose impression ( Fig. 97 ; si). Region just behind collar strongly and abruptly constricted, ventrally forming setose impression ( Fig. 97 ; si) filled with dense, unmodified setae. Mesoventral intercoxal process ( Fig. 97 ; msvp) long, narrow and weakly convex, nearly parallel-sided or indistinctly broadened near middle of mesocoxal cavities, fully separating mesocoxae, posteriorly fused with metaventrite or with variously distinct posterior tip. Mesanepisterna large and subtriangular; mesepimera ( Fig. 97 ; epm2) partly exposed in ventral view.

Mesonotum (illustrated in O'Keefe & Monteith (2002)) with subtriangular, elongate mesoscutellum with rounded apex, in intact specimens only its very tip visible between elytral bases; scutoscutellar suture absent.

Metanotum fully developed or somewhat reduced, with alacristae not or only slightly shortened; hind wings present or absent.

Metaventrite ( Fig. 97 ) short, subquadrate or subrectangular and slightly transverse, with lateral margins rounded; each mesocoxal cavity with posterior marginal carina, anterior margins not carinate; posterior margin of metaventrite deeply bisinuate laterally (in front of each metacoxa) and with a broad metaventral intercoxal process ( Fig. 97 ; mtvp) with variously deeply concave posterior margin and subtriangular posterolateral corners; metaventrite lacking foveae. External admetacoxal part of posterior metaventral margin with additional marginal thickening demarcated by a groove, forming adcoxal carina ( Fig. 97 ; acxc) at each side. Metanepisterna ( Fig. 97 ; aest3) broad and partly visible in ventral view, broadened posteriorly; metepimera broader than metanepisterna, with indistinctly demarcated inner and outer component, posteriorly extending far behind metacoxae. In one extinct species metaventrite with longitudinal median carina.

Metendosternite (metafurca) (illustrated in O’Keefe & Monteith (2000)) Y-shaped, with short but distinct stem and divergent lateral furcal arms.

Legs ( Figs 78–88 , 97 ) long and slender, often conspicuously so. Pro- and mesocoxa short subconical, metacoxa with nearly hemispherical basal part and subconical distal part. Mesocoxa lacking coxal bristles, but often with an elongate patch of thin long setae. All trochanters short and subtriangular. Femora weakly clavate, profemur typically with at least one conspicuously long and erect ventral seta (in some species with many such setae, as in Fig. 84 ; rarely setae reduced, as in Fig. 85 ). Tibiae robust, protibiae often curved in distal third or fourth. Tarsi long and slender, nearly subcylindrical, tarsomeres I–V subequal in length or reducing in length, tarsomere V strongly elongate, with curved and slender claws.

Elytra ( Figs 78–83 ) oval, strongly convex, with variously distinct humeral calli, lacking basal impressions, with rounded or pointed apices; elytral disc with distinct large and deep punctures arranged in six nearly complete and regular longitudinal rows. Elytra variously densely setose, setae typically long and erect.

Abdomen with sternite III not fused with metaventrite, about as long as sternites IV and V together; sternite VIII in male with rounded posterior margin.

Aedeagus (illustrated in Besuchet (1971), Jałoszyński ( 2009, 2018), Jałoszyński et al. (2003), O’Keefe & Monteith (2000), Orousset (2014), Zhou & Li (2015)) strongly elongate, with symmetrical median lobe, parameres heavily sclerotized, symmetrical or one longer than the other; flagellum simple, not coiled, but in many specimens broadened and forming a sac-like structure. Ejaculatory duct with elongate and narrow sperm pump, typically with funnel-like structures at both ends, but in some species with one or both funnels reduced. Aedeagus in repose positioned symmetrically inside abdomen, with basal orifice facing up.

Spermatheca (illustrated by the same authors as aedeagus) globular, variable in shape, in some species nearly spherical, in others elongate, thick-walled, with relatively large accessory gland.

Sexual dimorphism. In some species distinct, females often slightly smaller and with stouter elytra, or elytral apices in males and females differ in shape, or males have secondary sexual structures: modified protrochanters or protibial apices.

Characteristics. Larva. Body ( Figs 99–100 ) campodeiform, strongly elongate, subparallel-sided, narrowing posterad only in posterior half of abdomen, only slightly flattened, whitish with brown head and tergal plates, sparsely setose, setae long and unmodified. Head prognathous, weakly declines, with demarcated short, annuliform 'neck' and one pair of lateral stemmata; epicranial stem and frontal sutures distinct; nasale lacking teeth. Antenna longer than head and slender, all antennomeres cylindrical and not broadened, antennomeres I and II strongly elongate, antennomere III small but not vestigial, strongly elongate, longer than accessory appendage of antennomere II, the latter strongly elongate, spatulate. Mandibles falciform, moderately slender, pointed, each with one submedian mesal tooth; maxillary mala undivided, its apex densely setose, maxillary palp with all palpomeres elongate, palpomeres II and III comparable in length; labial palps with palpomere I longer than II, inserted on a long palpifer that resembles an additional palpomere. Thoracic tergites with well-defined tergal plates, ecdysial lines distinct. Abdomen with ten segments, all except X transverse; segment X elongate; urogomphi present, each composed of one elongate segment fused with posterolateral margin of abdominal segment IX; abdominal sternites weakly sclerotized, divided and bearing long setae. Legs long and slender. Spiracles annular, ventrolateral, nine pairs: one on mesothorax and eight pairs on abdominal segments I–VIII.

Composition and distribution. Clidicus includes 28 extant species distributed ( Fig. 89 ) in Asia ( China (Hainan), India (Karnataka, Tamil Nadu), Indonesia (Java, Kalimantan, Sumatra), Laos, Malaysia (Sabah, Sarawak), Philippines (Mindanao), Sri Lanka, Vietnam) and Australia (Queensland), and two extinct species from Cenomanian Myanmar amber (originally placed in Cretoleptochromus ). Two more extinct species were described and placed in Clidicus , one from Upper Eocene Baltic amber (Schaufuss 1896), the other from Lower Cretaceous Charentese French amber (Kirejtshuk et al. 2015); both are highly problematic and treated here as Mastigitae incertae sedis (see Remarks). Fossils of definitive Eocene Clidicus (remaining unnamed) are known from Baltic amber from Russia, the Kaliningrad Region (Jałoszyński et al. 2018).

Natural history. Species of Clidicus live in subtropical forests and most published records concerning collecting circumstances mention leaf litter as the source of specimens. Typical forest habitats of some species are shown in Figs 101–103 . One species, C. gracilipes Orousset, 2014 , was found in a cave, but it does not show any morphological adaptations typical of troglobitic beetles. Species that inhabit forests are encountered in small number of individuals or in large groups; the latter was the case for the Australian C. abbotensis O'Keefe, 2000 , which was found on trunks, logs and surrounding ground in large numbers, large groups were photographed inside small crevices in bark of logs ( Figs 104–105 ). Adults of this remarkable species has an aposematic pigmentation and are active during day, walking on the soil, mosses, logs and trunks of living trees; in the same environment larvae were found. Clidicus may feed on various small arthropods; O’Keefe & Monteith (2000) mentioned an individual of C. abbotensis observed walking with a neanurine springtail held in its mandibles.

Some species were believed to be associated with ants and termites, as adults were collected in association with some social insects or even from their open colonies. However, there are no signs of any particular morphological adaptations to myrmeco- or termitophily, and it seems that contacts of beetles with social insects are only occasional.

Remarks. Two extinct species were placed in Clidicus : C. balticus C. Schaufuss, 1896 , and recently C. cretaceus Kirejtshuk et al., 2015 . The former species comes from the Upper Eocene Baltic amber and was described inadequately, without any illustrations. It may, or may not belong to Clidicus ; the type specimen has been lost (very likely destroyed) during World War II, and it is not possible to verify placement of this species. Clidicus cretaceus was described on the basis of a specimen found in the Lower Cretaceous Charentese (French) amber, and although illustrations given by authors show a beetle that very likely could be a true Clidicus or Clidicus -like scydmaenine, it was described in a way that raises doubts about its placement. The metacoxae were described as contiguous and transverse, characters that do not occur in any Mastigitae, which all have broadly separated metacoxae which are longer than broad or with length subequal to width. The abdomen was described as having five ventrites, a character not known in any Scydmaeninae , which always have six abdominal segments visible in ventral view, although in some genera the suture between sternites VII and VIII may be indistinct (but not in Mastigitae). Moreover, the specimen in lateral view was illustrated with an enormously large eye much closer to the posterior head margin than to the mandibular base, which, again, is a character not known in any Mastigitae; and the 'neck' region of C. cretaceus was illustrated in profile as higher than the anterior part of the head capsule, which is a condition not known in Clidicus , in which the height of the 'neck' region seen in profile is smaller than the height of the anterior part of the head. Either the authors misinterpreted some characters, or this species does not belong in Scydmaeninae . These two species are treated here as incertae sedis, with C. balticus maintained within Mastigitae, and C. cretaceus being incertae sedis within Coleoptera .

All nominal extant species were adequately described or redescribed by Besuchet (1971), Jałoszyński ( 2009,

2018), Jałoszyński et al. (2003), Orousset (2014), and Zhou & Li (2015).

Figures

FIGURE 89. Clidicini, distribution of extant species of Clidicus.

FIGURES 78–83. Clidicini, examples of extant genera; dorsal (78, 80, 82) and lateral (79, 81, 83) habitus. Clidicus gracillipes (78–79); Clidicus bellator (80–81); Clidicus formicarius (82–83).

FIGURES 84–85. Clidicini, examples of extant species; anterior portion of body, ventral. Clidicus formicarius (84); Clidicus abbotensis (85). Arrows showing outstanding setae on head, profemur and prothoracic hypomera, which are largely reduced in C. abbotensis.

FIGURES 90–93. Clidicini, morphological structures, Clidicus bellator. Head in dorsal (90) and ventral (91) views; mouthparts in dorsal view (92); left maxillary palpomeres III–IV in dorsal view (93). Abbreviations: ai, antennal insertion; bst, basistipes; cd, cardo; cl, clypeus; fcg, frontoclypeal groove; gal, galea; gp, gular plate; hr, hypostomal ridge; lac, lacinia; lbr, labrum; lhl, lateral hypopharyngeal lobe; lp, labial palp; mn, mentum; mst, mediostipes; mxp1–4, maxillary palpomere I–IV; pmn, prementum; ppf, palpifer; ptp, posterior tentorial pit; smn, submentum.

FIGURES 94–98. Clidicini, morphological structures, Clidicus bellator. Mouthparts in ventral view (94); left scape and pedicel in ventral view (95); prothorax in ventral view (96); pterothorax and first visible abdominal sternite in ventral view (97); aedeagus and sperm pump (98). Abbreviations: acxc, adcoxal carina; ade, adcoxal expansion; aed, aedeagus; aest3, metanepisternum; ar, anterior ridge; bst, basistipes; bstr, basisternal part of prosternum; cd, cardo; dej, ductus ejaculatorius; epm2, mesepimeron; gal, galea; lac, lacinia; lhl, lateral hypopharyngeal lobe; lp1–3, labial palpomere I–III; mn, mentum; mst, mediostipes; msvp, mesoventral intercoxal process; mtvp, metaventral intercoxal process; pd, pedicel; pm, prementum; ppf, palpifer; pre, prepectus; sc, scape; si, setose impression; spp, sperm pump; st3, abdominal sternite III; v3, metaventrite.

FIGURES 86–88. Clidicini, examples of extinct species; lateral (86), ventral (87) and lateroventral (88) habitus. Palaeoleptochromus schaufussi (86; Upper Cretaceous of Canada; photo Brendon Strilisky); Clidicus archaicus (87; Upper Cretaceous of Myanmar); Clidicus sp. (88; Upper Eocene of Europe).

FIGURES 99–100. Clidicini, larva of Clidicus abbotensis in dorsal (99) and ventrolateral (100) views.

FIGURES 101–106. Clidicini, habitats (101–103) and adults in nature (104–106). Dam B'Ri Waterfall, Vietnam, habitat of Clidicus bellator (101–102; photo Shûhei Nomura); Mt. Abbot, Australia, habitat of Clidicus abbotensis (103–106; photo Geoff Monteith).