Dineutus (Rhomborhynchus), Ochs, 1926

Gustafson, Grey T. & Miller, Kelly B., 1835, Revision of the Southeast Asian Whirligig Beetle GenusPorrorhynchusLaporte, 1835 (Coleoptera: Gyrinidae: Gyrininae: Dineutini), The Coleopterists Bulletin 1835 (4), pp. 675-714 : 675-714

Subgenus Rhomborhynchus Ochs, 1926

Dineutus (Rhomborhynchus) Ochs 1926: 65 [original description], 1955: 130;

Porrorhynchus (Rhomborhynchus) : Guignot 1950: 124 [new status]; Brinck 1955: 103 [status change]; Polhemus 2011: 52 [minor description, habitat].

Type Species. Porrorhynchus depressus Régimbart, 1902 by original designation of Ochs 1926: 65.

Diagnosis. Medium sized whirligig beetles: 9–11 mm. Antennal flagellum with six flagellomeres ( Fig. 2D ). Labrum ventrally with longitudinal line of setae paramedially. Dorsal eye situated posteriorly with posterior margin located in plane with that of ventral eye. Gular suture complete. Pronotum with transverse impressed line. Elytral margin without significant swelling associated with reception of fore leg. Males without protrochanteric setose patch. Profemur without two linear series of large setose clusters, only with a single linear series of small setose clusters on posterior margin of ventral face; anterior face of profemur with setigerous punctures. Posterior face of protibia with golden setose brush limited to distal tenth. Posterior face of ultimate protarsomere in female without setose furrow, completely glabrous.

Description. Head: Antenna with 6 flagellomeres; pedicel broad, nearly rectangular in form. Labrum ventrally with 2 transverse, linear, setose rows in basal 1/2, and an additional longitudinal row anteriad 2 basal transverse rows, running near entire length of labrum, situated paramedially. Gular suture complete, lateral arms of gular suture meeting anterolateral margin of ventral epicranium posteriad submentum. Thorax: Pronotum with transverse impressed line, situated close to anterior margin of pronotum, running parallel with it, nearly meeting anteromedially, weakly effaced medially. Elytral lateral margin without significant swelling at mid-length associated with depressed cavity in meso- and metaventrite that receives fore leg, elytra evenly deflexed throughout. Protrochanter of male without setose patch, posterior face completely glabrous, ventral face of males and females with linear series of short, sharp setae in distal third; profemur ventrally with linear series of small setose clusters on anterior margin only, running only basal 1/3–1/2 of profemur, setose patches composed of 1 to few long setae, ventral surface with excavation apically for reception of protibia, anterior and posterior margins of ventral surface with series of knobs, especially apically, posterior face covered with short stout setae in recessed pits, as well as linear series of setigerous punctures (4–6), seta of setigerous punctures long and narrow, ventral margin of anterior face basally with series of short setae in basal 1/2, posterior face with warty bumps situated basally and towards ventral margin, mostly glabrous; posterior face of protibiae with setose brush limited to distal ca. 1/10 length of tibia; posterior face of protarsomere V of female without setose furrow, posterior face entirely glabrous. Elytra with striae very faintly visible. Metaventral wing in the form of isosceles triangle. Metacoxal wing obliquely transverse, evenly arcuate, metacoxal wing ending at apical 1/9 of metanepisternal length. Abdomen: Abdominal sternite VIII weakly emarginate medially. Male genitalia with median lobe of aedeagus not broadly articulating basomedially with parameres, parameres with narrow basal bridge, longitudinal lists of medial lobe very narrow, lateral lists not meeting medial list.

Sexual Dimorphism. No significant size or shape dimorphism is evident. Profemoral setation three tufts of setae, whereas females tend to have four or more.three tufts of setae, whereas females tend to have four or more.

Figures

Fig. 2. Porrorhynchus species, right antenna (anterior view above, posterior view below. A) P. landaisi, B) P. indicans, C) P. marginatus, D) P. depressus. Scale bars = 0.5 mm.