Scydmaenus (Corbulifer) Franz

Scydmaenus (Corbulifer) Franz

Scydmaenus (Corbulifer Franz, 1975): 286 (as subgenus of Scydmaenus). Type species: Scydmaenus tamborinensis Franz, 1975 (des. orig.).

Revised diagnosis. Scydmaenus with posteroventral region of head capsule (bearing posterior tentorial pits) laterally confluent with genae and postgenae; entirely obliterated notosternal sutures; present hypomeral grooves; lacking basal elytral foveae; apices of parameres free, forming a pair of apical projections; protarsi not broadened in males; and metatibiae strongly modified (broadened) in males.

Redescription. Body ~ 2 mm in length, body shape (Figs 17, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51) uniform, 'ant-like', i.e., constricted between head and pronotum and between pronotum and elytra, with flattened head, moderately convex pronotum and moderately to strongly convex elytra; pigmentation uniformly brown, typically with slightly reddish or chestnut hue; vestiture of setae moderately dense and composed of thin, suberect to erect setae.

Head (Fig. 1) divided into a large exposed anterior part and a much smaller posterior 'neck' region, the latter retracted into prothorax. Anterior part short, subquadrate or indistinctly subtrapezoidal, flattened; eyes small, 2–5 times shorter than tempora, weakly convex, finely faceted, narrowly but clearly separated from mandibular bases; tempora weakly convergent posterad, anteriorly weakly rounded, posteriorly strongly bent mesad at an obtuse angle; vertex and frons confluent, convex, except for a shallow posteromedian impression on vertex; occipital constriction broader than half width of head. Labrum (Fig. 2) strongly transverse, anterior and lateral margins with nine shallow and broad emarginations, so that labral margin appears dentate; dorsal surface with paired, sparsely and symmetrically distributed setae of various lengths; ventral surface (epistome) with several (typically seven) long and thick sensilla inserted near labral base and one pair of much shorter peg-like sensilla inserted slightly behind the long ones. Mandibles (Fig. 3) large and robust, subtriangular and slightly asymmetrical, each with one mesal tooth (Fig. 3; mt) with bifurcate apex, larger and more deeply divided on the right mandible, setose prostheca (Fig. 3; pst) present and long, with its proximal half composed of particularly dense setae. Maxillae (Fig. 1) generalized, as in most Scydmaeninae, with short and broad cardo (Fig. 1; cd), subtriangular basistipes (Fig. 1; bst), elongate mediostipes (Fig. 1; mst), elongate palpifer (Fig. 1; ppf) and elongate galea (Fig. 1; gal) and lacinia (Fig. 1; lac). Maxillary palps (Fig. 1) moderately large, not different from those in Scydmaenus s. str. Submentum (Fig. 1; smn) short and broad, anteriorly deeply emarginate; mentum (Fig. 1; mn) subtrapezoidal, slightly broader than long, anteriorly emarginate; prementum (Fig. 4; pmn) large, with anterior margin subtriangular and projecting anterad, insertions of labial palps broadly separated. Labial palpomere II (Fig. 4; lp2) much longer than I and much broader than III. Gular plate (Fig. 1; gp) broad and distinctly microreticulate, gular sutures indistinct; posterior tentorial pits (Fig. 1; ptp) small, elongate, located in front of transverse impression demarcating the 'neck' region ventrally.

Antennae (Fig. 5) shorter than body, slender, with antennomeres VII and VIII distinctly asymmetrical, with their mesal margins shorter than external lateral margins; antennomeres IX–XI forming a trimerous club.

Pronotum in dorsal view oval, broadest slightly behind anterior third, weakly elongate; all margins rounded, anterior and posterior pronotal corners strongly obtuse and rounded; pronotal base with two pairs of very small, shallow and often diffuse antebasal pits, distance between median pits several times larger than that between each median and lateral pit.

Prosternum (Fig. 6) with its basisternal part (Fig. 6; bst) very short, less then half as long as coxal part; prosternal process (Fig. 6; psp) developed as a short longitudinal ridge, which is very weakly elevated and in intact specimens hidden between contiguous procoxae; notosternal sutures entirely absent, prosternum laterally completely fused with hypomera; hypomera (Fig. 6; hy) lacking hypomeral ridges, but with distinct posterior hypomeral grooves (Fig. 6; hg).

Mesonotum (Fig. 7) with strongly elongate mesoscutum (Fig. 7; sc2) indistinctly delimited from subtriangular mesocutellum (Fig. 7; scl2), scutoscutellar suture absent; in intact specimens scutellum not visible between elytral bases.

Mesoventrite (Fig. 8) with narrow and sharply demarcated anterior ridge (Fig. 8; ar); area behind ridge functioning as a procoxal rest (Fig. 8; pcr) flattened and asetose, not divided at middle, posteriorly demarcated by a sharp stepwise transverse edge, region behind the edge impressed and densely setose; mesoventral intercoxal process (Fig. 8; msvp) carinate, weakly elevated, with a distinct posterior tip.

Metanotum with alacristae reaching half length of metascutum; hind wings present.

Metaventrite (Fig. 8) slightly broader than long, with rounded sides; metanepisterna (Fig. 8; aest3) very broad and shifted ventrad, entirely exposed in ventral view in intact specimens; metaventral intercoxal process (Fig. 8; mtvp) short and broad, with small median lobe projecting caudad and lateral corners also projecting caudad.

Elytra oval, lacking basal foveae and humeral denticles, anterior margin of elytron (adjacent to elytral articulating lobe (Fig. 7; eal)) slightly concave.

Legs moderately long and robust; metatrochanters (Fig. 8; tr3) strongly elongate; other podites as in Scydmaenus s. str., except for different male dimorphic structures (see below).

Abdomen short, with first visible sternite clearly longer than second; suture between V and VI distinct; pygidium and propygidium (Fig. 9; pg, prpg) exposed, propygidium with its posterodorsal margin forming lateral denticles or lobes.

Spermatheca (Fig. 10) located deeply in abdomen, asymmetrical, nearly hemispherical with 'basal' surface impressed and bearing a broad subconical projection with distally located insertion of ductus spermathecae and a small weakly sclerotized accessory gland (Fig. 10; acg) connected with spermatheca by a broad duct.

Aedeagus (Figs 15–16) symmetrical, strongly elongate and curved or recurved in lateral view, basal foramen (Fig. 15; bf) close to base of median lobe on its dorsal surface; ostium (Fig. 16; ost) subapically on dorsal wall, in all species flanked by variously shaped but always strongly elevated and typically asymmetrical lateral flanges (Fig. 16; lf); parameres (Fig. 15; pm) fused with aedeagus, but fusion sites marked by shallow furrows, apices of parameres free and forming apical projections (Fig. 16; app) of aedeagus, parameral subapical setae forming two longitudinal dorsal rows on aedeagal apex, additionally dorsal wall of median lobe slightly in front of ostium with oblique or transversely arcuate rows of setae; endophallic structures asymmetrical, some of the sclerites protruding from ostium, among them a subtriangular copulatory piece (Fig. 16; cp), which is movable and can flip so that its tip can be directed dorsad or dorsoproximad.

Sexual dimorphism profound; males of all species have strongly, often monstrously modified metatibiae (Figs 11–12, 55–65), which are abruptly or gradually broadened, and typically with a glandular dorsolateral, lateral or/ and ventral 'pocket'; in species lacking the 'pocket' a group of tiny pores can be seen in a submedian dorsal or dorsolateral region; 'pocket' is often accompanied by a group of conspicuously long setae. In one species also elytra are modified in males, with glandular subapical structures (a flattened area with a convexity, both bearing modified setae). Eyes in males are typically larger than those in females (except for one species). Protarsomeres in males are not broadened, and in both sexes tarsomeres I–III bear spatulate adhesive setae.

Distribution and composition. Corbulifer comprises 10 species (2 known previously and 8 described as new) distributed in forests along the eastern coast of Australia.

Remarks. Characters of the type species of Scydmaenus s. str. were studied and illustrated by Jałoszyński (2016). Corbulifer differs from Scydmaenus s. str. in the following characters: posteroventral region of head capsule, on which the posterior tentorial pits are located, laterally confluent with genae and postgenae (in Scydmaenus s. str. developed as an elevated 'platform' laterally demarcated by stepwise ridges); notosternal sutures entirely obliterated (in Scydmaenus s. str. vestiges of sutures can be seen at the anterior prosternal margin); elytra lacking basal foveae (in Scydmaenus s. str. each elytron with a pair of small and in some species poorly visible foveae); apices of parameres free, forming a pair of apical projections (parameral apices fused with the median lobe in Scydmaenus s. str.); protarsi not broadened in males (in Scydmaenus s. str. distinctly broadened); and metatibiae strongly modified in males (in Scydmaenus s. str. unmodified). However, character variability remains poorly studied among species of Scydmaenus s. str. and all other subgenera of Scydmaenus, and consequently the diagnosis of Corbulifer (and all other subgenera) as well as the subgeneric division of Scydmaenus may change in future.