Mastigus Latreille
Creators: name: Paweł Jałoszyński
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Mastigus

description: Mastigus Latreille
Mastigus Latreille, 1802: 17. Type species: Ptinus spinicornis Fabricius, 1787 (virtual monotypy and des. Latreille, 1810: 427). Australostigus Leleup, 1968: 42. Type species: Ptinus spinicornis Fabricius, 1787 (des. orig.). Synonymized by Newton &
Franz (1998).
Diagnosis. Unclearly diagnosed genus; within Mastigini identifiable on the basis of a combination of subtriangular mesoventral intercoxal process with narrow and pointed or narrowly rounded tip (Fig. 171; msvp) and the aedeagus with the short paramere distinct, always delimited from the long paramere by at least subtriangular or rounded emargination (but see Remarks).
Characteristics. Adults. Body (Figs 153–154) large, 3.50̄ 6.80 mm in length, with dark brown or nearly black head, similarly dark or yellowish-brown pronotum, and elytra brown, often with reddish or yellowish hue, strongly convex, dorsally densely but finely setose, setae unmodified except for long and thick bristles on scape and pedicel.
Head capsule (Figs 167–168, 172) divided into large and exposed anterior part and much smaller, subcylindrical 'neck' region retracted into prothorax and demarcated by distinct occipital constriction; 'neck' region much broader than half width of head. Anterior part of head flattened, subequal in width with prothorax, distinctly elongate, broadest near middle. Composite eyes dorsolateral, moderately large, composed of numerous small ommatidia, weakly projecting from the silhouette of the head, broadly separated from mandibular bases. Vertex and frons divided by a distinct median longitudinal groove (Fig. 167; mg); vertex strongly transverse, convex at sides, with posterior margin slightly concave. Tempora much longer than eyes, weakly rounded. Frons between antennal insertions not forming a demarcated 'platform', weakly convex or flattened, anteriorly demarcated by a deep and very short frontoclypeal groove largely obliterated at sides. Clypeus very short and broad, with nearly straight sides, slightly convergent anterad or parallel. Antennal insertions located anterodorsally, relatively narrowly separated. Gular plate (Fig. 172; gp) lacking sutures, indistinctly transversely reticulate; posterior tentorial pits (Fig. 172; ptp) oval, in front of broad and diffuse transverse impression demarcating 'neck' region ventrally; hypostomal ridges (Figs 177, 224; hr) arcuate, posteriorly reaching middle between anterior submental margin and posterior tentorial pits. Head finely to strongly punctate, densely setose.
Antennae (Figs 153–154, 168–170) long and slender, shorter than body; scape (Figs 168–169; sc) 5–6 times as long as broad, thickened, broadest in front of middle, much longer than head, with lateroventral (more ventral than lateral) emargination; pedicel (Figs 168–169; pd) enlarged, slightly to much shorter and narrower than scape, 5–8 times as long as broad, broadening from narrow base to subapical region. Both scape and pedicel with two ventral longitudinal rows of several long and thick bristles with papillate insertions, area between bristles with variously densely distributed porous fields (Fig. 170; pf); antennomeres III–XI distinctly narrower than pedicel, elongate, each slightly thickened distad, basal stalks not exposed in intact beetles, basal rings absent or indistinct; antennomere XI elongate and indistinctly asymmetrical. Antennomeres covered with variously dense, long setae; surface of antennomeres smooth.
Mouthparts. Labrum (Fig. 167) strongly transverse, with lateral margins slightly convergent anterad and weakly rounded, and with anterior margin weakly concave, with a pair of broad and short sublateral teeth broadly separated at middle by a very shallow emargination, and with two partly irregular transverse rows of long and short setae. Mandibles symmetrical, subtriangular and robust, each with one mesal dorsal tooth and a group of 3 mesal ventral teeth, setose prostheca long. Maxilla (Figs 172–173) with large cardo (Fig. 173; cd); basistipes (Fig. 173; bst) subtriangular and elongate; mediostipes (Fig. 173; mst) large and sharply demarcated from lacinia and galea (Fig. 173; gal), which are both elongate and each with dense group of thin distal setae; palpifer (Fig. 173; ppf) broad and elongate; maxillary palp slightly to much longer than head capsule, composed of minute palpomere I (Fig. 172–173; mxp1), slender, curved, distinctly but only slightly broadening distad palpomere II (Figs 167–168, 172; mxp2), palpomere III (Figs 167–168, 172; mxp3) strongly elongate, strongly and gradually broadened distad, with transverse distal margin, palpomere IV (Figs 167–168, 172) shorter than III, approximately subtriangular and broadening distad. Labium (Figs 172–173) with broad and short submentum (Fig. 172; smn) posteriorly not demarcated from gular region, densely setose and lacking an outstanding pair of anterior or subanterior lateral setae; mentum (Fig. 173; mn) subtrapezoidal and strongly transverse, with anterior margin very deeply emarginate, so that anterolateral corners form triangular and usually pointed lobes projecting anterad; prementum (Figs. 173; pm) long, subtrapezoidal, broadest distally, lacking demarcated ligula, with several pairs of submedian anterior setae, with broadly separated bases of labial palps; lateral hypopharyngeal lobes moderately large; labial palp composed of three palpomeres: palpomere I (Fig. 173; lp1) small, elongate, strongly broadening distad, palpomere II (Fig. 173; lp2) largest, conspicuously enlarged, long and broad, approximately barrel-shaped, palpomere III (Fig. 173; lp3) very small and narrow in relation to III, as long as about half length of III and very narrow, pointed.
Prothorax (Figs 153–54, 174) elongate, strongly convex but with flattened dorsum, broadest near anterior third. Pronotum with anterior and posterior margins arcuate, sides rounded in anterior half and sinuate in posterior half; anterior and posterior corners obtuse-angled; pronotal base lacking pits and groove. Prosternum (Fig. 174) with basisternal part (Fig. 174; bstr) indistinctly shorter than coxal part. Prosternum laterally completely fused with hypomera. Coxal region anteriorly and laterally without marginal carina; postcoxal hypomeral lobes (Fig. 174; pchl) conspicuously large, rounded and strongly projecting anteromesad and overlapping with (but not fused to) posterolateral lobes of prosternum, so that procoxal cavities are not open, but entirely delimited posteriorly by hypomeral lobes. Prosternal intercoxal process developed as a narrow and weakly elevated carina in intact beetles hidden between procoxae. Ventral surface of prothorax densely setose.
Mesoventrite (Figs 171, 175) subtrapezoidal, broadening posteriorly. Prepecti moderately long and together with anteromedian mesoventral area forming a relatively short 'collar', which is weakly impressed just behind its anterior ridge, anterior margin of impression with a short subtriangular posteromedian projection. Impressed area shallow, short and diffuse, with median sternal area behind it becoming gradually convex caudad. Mesoventral intercoxal process (Figs 171, 175; msvp) reaching middle of mesocoxal cavities; short and very broad, subtriangular, weakly convex, broadly separating mesocoxae, posteriorly separated from anterior metaventral process, with its posterior margin subtriangular. Mesanepisterna relatively narrow and strongly elongate, demarcated from median part of mesoventrite by a distinct ridge and from mesepimera by complete suture; mesepimera elongate, indistinctly demarcated from metepimera, not exposed in ventral view.
Mesonotum with cordiform, broad mesoscutellum pointed at apex, in intact specimens not visible between elytral bases; scutoscutellar suture absent.
Metanotum partly reduced, with lightly sclerotized mesoscutum, but only slightly shortened alacristae; hind wings absent.
Metaventrite (Figs 171, 175) short, subrectangular and strongly transverse, with lateral margins rounded; mesocoxal cavities with all margins non-carinate; posterior margin of metaventrite deeply bisinuate laterally (in front of each metacoxa) and with a broad metaventral intercoxal process with shallowly concave posterior margin; anteriorly metaventrite forming a short anterior metaventral process (Figs 171, 175; amvp) similar in shape to mesoventral intercoxal process and meeting the latter at middle of mesocoxal cavities; metaventral foveae absent. External admetacoxal part of posterior metaventral margin lacking adcoxal carinae, but with adcoxal expansions. Metanepisterna relatively narrow, partly visible in ventral view, narrowing posteriorly; metepimera 2–3 times as broad as metanepisterna, with not demarcated inner and outer components, posteriorly extending far behind metacoxae.
Metendosternite (metafurca) with stem much broader than long and broadly separated, divergent lateral furcal arms, lacking median longitudinal projection.
Legs (Figs 153–154, 171, 174–175) long and slender. Pro- and mesocoxa short subconical, metacoxa with nearly hemispherical basal part and subconical distal part. Mesocoxa lacking coxal bristles. All trochanters short and subtriangular; femora weakly clavate; tibiae slender; tarsi long and slender, nearly subcylindrical, tarsomeres I–V reducing in length, tarsomere V strongly elongate, with curved and slender claws lacking elongate costae; empodial region was not studied.
Elytra (Figs 153–154) oval, strongly convex, lacking humeral calli and basal impressions, with rounded apices; elytral disc with barely discernible incomplete and superficial longitudinal rows of fine punctures, in some species obscured by very fine transverse striae; microsculpture fine. Elytra densely setose, setae short and nearly recumbent.
Abdomen (Fig. 171) with sternite III firmly fused with metaventrite, much longer than sternite IV, but shorter than IV–VI together; sternite VIII in male distinctly, often deeply emarginate.
Aedeagus (illustrated in Jałoszyński (2012c), Jałoszyński et al. (2018), Leleup (1968)) moderately elongate, with asymmetrical median lobe and asymmetrical parameres, one shorter than the other; flagellum very long and forming several coils. Ejaculatory duct with elongate and narrow sperm pump lacking funnel-like structures. Aedeagus with elongate copulatory piece with membranous endophallus permanently everted, and only inflated during copulation, with distal end of flagellum permanently fixed, so that flagellum is not extricable. Aedeagus in repose positioned asymmetrically inside abdomen, with basal orifice lateral or dorsolateral.
Spermatheca subglobose, with relatively large accessory gland.
Sexual dimorphism distinct, females distinctly larger and with relatively broader elytra than males; males with emarginate, females with rounded sternite VIII.
Larva. Unknown.
Composition and distribution. Mastigus comprises five species distributed in west-southern part of the Republic of South Africa (western West Cape Province) (Fig. 164).
Natural history. Almost nothing is known about natural history of these beetles. They are rarely collected, typically by using pitfall traps, often near the coastline, on sandy places with sparse vegetation. Judging from a similar body form and structures, Mastigus species may resemble Palaeostigus and Stenomastigus in diurnal, open life style. However, all species were described on the basis of a few specimens only, and Leleup (1968), who in his large monograph of South African Mastigini included hundreds of specimens of Palaeostigus and Stenomastigus, also found only a small number of adult Mastigus during his field studies. It seems that species of Mastigus do not live in such large populations as Palaeostigus and Stenomastigus.
Remarks. Mastigus is currently the most problematic genus of Mastigini, comprising species that show the greatest diversity in structures of the aedeagus. Species of Mastigus have a general appearance more similar to that of Palaeostigus than Stenomastigus; the latter genus includes species very slender and with extremely long legs and antennae, with coarse microgranulation of the elytra, whereas Mastigus and Palaeostigus share a stouter body form, less elongated appendages and either shiny or matt but always not coarse elytral surface. Consequently, Mastigus can be distinguished from Stenomastigus solely by its general body shape. However, fine morphological structures of these two genera are nearly identical and a major difference can be found only in the aedeagus. In Mastigus the aedeagus is distinctly stouter and shorter than that in Stenomastigus, the short paramere is always developed and demarcated from the long paramere by a subtriangular or rounded emargination, so that the apex of short paramere is distant from the lateral margin of the long paramere. Also the capsular, basal part of the aedeagus that contains flagellar coils is larger in relation to the parameral part in Mastigus than in Stenomastigus. In the latter genus the aedeagus is typically very narrow and long, with one paramere strongly elongate and the other one usually absent. However, in few cases the short paramere is present, but its apex overlaps with the lateral margin of the long paramere or it is very indistinctly demarcated. Aedeagi of Mastigus species are diverse in shapes and structures and this genus must be revised to clarify its separate placement.
Palaeostigus, although very similar to Mastigus, differs clearly in the shape of the mesoventral intercoxal process, which is not subtriangular but subtrapezoidal and its posterior margin is nearly straight and widely separates mesocoxae; and in a deep mesoventral setose impression, which is absent in Mastigus.
All species were treated by Leleup (1968) and Jałoszyński (2012c); two species originally placed in Mastigus were treated as incertae sedis within Mastigini by Leleup (1968).
description: Published as part of Paweł Jałoszyński, 2018, World genera of Mastigitae: review of morphological structures and new ecological data (Coleoptera: Staphylinidae: Scydmaeninae), pp. 1-119 in Zootaxa 4453 (1) on pages 83-86, DOI: 10.11646/zootaxa.4453.1.1, http://zenodo.org/record/1454920