Paroxythyreus, Jacobs, 2025

Jacobs, Dawid H., 2025, Paroxythyreus stilleri, a new genus and species of South African Macrocephalini (Hemiptera: Heteroptera: Reduviidae: Phymatinae) with a note on the metathoracic glands and their evaporation areas in the Reduviidae, Zootaxa 5719 (1), pp. 108-116 : 109-111

Paroxythyreus gen. nov.

Type species: Paroxythyreus stilleri sp. nov.

Diagnosis. The male of the new genus (female currently unknown) can be recognized by the following combination of characters: scutellum reaching the apex of the corium with two small sub-median lobes apically ( Figs 1 , 8 ); humeral angles of the pronotum ordinary, obtuse, not elevated or provided with projections; head parallel-sided with small eyes and small ocelli which are situated about halfway on the postocular portion; antennae with the 4th joint long and cylindrical, nearly 5 times as long as the first joint; abdomen expanded but longer then wide ( Figs 1–3 ).

Description. Macropterous male, abdomen longer than its maximum width. General facies ( Figs 1–3 ) as typical for the Macrocephalini .

Integument and vestiture. Integument dull; head, first 3 antennal joints, anterior lobe of pronotum, all thoracic pleura, abdomen above and below granulate, granules bearing short adpressed setae; posterior lobe of pronotum, scutellum and coria punctate; 4th antennal joint densely covered with short, sharp, apically directed Setae of variable thickness ( Figs 12–13 ).

Head parallel sided in dorsal view, preocular and postocular portions subequal in length, eyes small and only weakly protruding laterally; ocelli small, situated about halfway on postocular part of head, just medially of the eyes, separated by median furrow of head; bucculae small, meeting in front of the labium, continuing posteriad as a pair of parallel longitudinal sharp and irregular ridges next to labium for entire length of head; labium with first joint robust, longer than joints 2 and 3 taken together, all 3 joints tapering apicad, ultimate joint short and thin ( Fig 5 ); antenna robust, insertion of 1st joint obscured in lateral view by antennal sclerite produced anteriad, 1st joint thick, distinctly longer than its width; 2nd and 3rd joints thinner and shorter: 2nd barrel shaped, slightly longer than wide, bearing a short but prominent trichobothrium; 3rd bead shaped, shorter than wide; 4th very long, cylindrical with about the same diameter over its length, nearly as thick as the 1st and more than 4 times as long.

Thorax. Dorsum. Pronotum with anterior lobe roughly trapezoid, anterior margin concave with sharp anterolateral angles; posterior lobe roughly transversally hexagonal, longer than anterior lobe, humeral angles simple, obtuse, not elevated. Scutellum longer than broad, lateral margins somewhat converging, reaching to level of corial apex, rounded but with a pair of small lobes at apex, giving it a bifid appearance, lateral margins strongly thickened to form black costae becoming narrower and lower posteriad and fading near the apex. Hemelytra well developed, corium with Sc, R+M and Cu veins well developed, apex tapering to a point; membrane with R bifurcating not far behind apex of corium, M simple, Cu and PCu connected by a crossvein to form a basal cell; a nearly straight fracture visible between R and M. Legs. Fore leg typical for Macrocephalini with a long coxa, trochanter ordinary; femur about 1.6 times longer than coxa with distal half dilated and ventrally flattened and rounded, rounded part with two rows of small, short, thick, blunt pegs, near proximal end of inner row is a small lobe with a peg at its apex, just mesal of inner row are 6 long sensory setae; tibia falcate, perfectly fitting rounded part of femur, narrowing evenly to a sharp apex, with pegs (roughly similar to those of femur) on its outer ventral surface, inner side with a tibial comb present just proximad to middle consisting of about 12 closely set stiff setae; tarsus absent. Mid and hind legs short but hind legs somewhat longer than mid legs, in both femur and tibia of subequal length, tarsus distinctly shorter than tibia, with two joints, first joint short, second joint long, more than 3 times longer than first joint, bearing two claws and two parempodial setae apically.

Venter. Prosternum small, with a deep median stridulatory groove and posteriorly open coxal cavities; laterally fused with propleura which are strongly and pointedly produced anteriad anteroventrally to give a deep bifid appearance to anterior margin; mesosternum with a large median somewhat rectangular area to accommodate procoxae in rest ( Fig. 5 ); metapleuron with a small area of modified cuticle just behind and laterad of opening of metathoracic spiracle ( Figs 9, 10 , 15 ).

Abdomen dilated, longer (measured from level of anteriormost part of segment 2) than broad, greatest width across segment 4; laterotergites and laterosternites completely fused with their respective mediostergites and - sternites, the colour pattern, and in case of laterosternites, a longitudinal ridge indicates their boundaries; apical segment broadly and shallowly excavate ( Fig. 7 ; not visible in Figs 1 and 2 because apex of abdomen is somewhat upturned); mediosternites 3–6 with subtriangular median sclerites, becoming wider posteriad ( Fig. 2 ); spiracles on segment 1 dorsal (covered by the wings), on segments 2–7 situated on small sublateral protuberances on their respective mediosternites at about a third of length of segments; pygophore obovate, slightly longer than wide.

Diversity and distribution: The genus is currently monotypic and the single included species is only known from the holotype which was collected high in the Drakensberg range (~ 3050 masl) in South Africa near the Lesotho border ( Fig. 11 ) .

Etymology. The name of the new genus is composed from the latinized Greek prefix para- (= close to, next to, near) and the generic name Oxythyreus , indicating the close relationship between the two genera; gender masculine.

Discussion. Paroxythyreus is virtually identical to Oxythyreus in the majority of morphological characters and I considered to describe it in that genus. However, that would have been in conflict with the main diagnostic feature of Oxythyreus , namely the acute and usually short scutellum (although there seems to be variation in the length of the scutellum which in O. cylindricornis schuhi Van Doesburg & Pluot-Sigwalt, 2007 seems to almost reach the level of the corial apex and the middle of the fifth abdominal segment) without any lobes apically. I have thus decided to describe it as a new genus.

The presence of apical lobes of the scutellum is an unusual feature, but similar lobes also occur in Doesburgella dilatata Rédei & Jindra, 2013 , which is apparently not particularly closely related to Paroxythyreus . Interestingly these lobes are somewhat asymmetrical in P. stilleri sp. nov., and judging by the photo of the holotype, also slightly so in D. dilatata .

Figures

FIGURE 11. Map showing the type locality (star) of Paroxythyreus stilleri gen. & sp. nov.

FIGURES 1–4. Paroxythyreus stilleri gen. & sp. nov., holotype, male. 1, dorsal view; 2, ventral view; 3, lateral view; 4, labels.

FIGURES 5–10. Morphological aspects of Paroxythyreus stilleri gen. & sp. nov. and Oxythyreus cylindricornis (Westwood, 1841). Figs 5–8, P. stilleri gen. & sp. nov.: 5, ventral view of the prothorax and the head; 6, fore femur and tibia; 7, apex of the abdomen showing its slight excavation; 8, scutellum. Figs 9–10, O. cylindricornis (Westwood, 1841): 9, lateral view of the meso- and metathorax and first abdominal segment; 10, same, with the wings removed. Lettering: EMF = metepimeral furrow; ESD = metepisternal depression; MC = modified cuticle on metapleuron; MSP = opening of the metathoracic spiracle; MSW = mesothoracic wing; SP1 and SP2 = abdominal spiracles 1 and 2; TC = tibial comb.

FIGURES 12–16. SEM photos of O. cylindricornis (Westwood, 1841): 12, part of the 4th antennal joint showing the two types of setae; 13, same at greater magnification; 14, fore tibia showing the tibial comb; 15, lateral view of the meso- and metathorax with the wings removed; 16, structure of the modified cuticle on the metapleuron. Lettering: EMF = metepimeral furrow; ESD = metepisternal depression; MC = modified cuticle on metapleuron; MSP = opening of the metathoracic spiracle.