Porrorhynchus Laporte, 1835

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

Porrorhynchus Laporte, 1835

Trigonocheilus Dejean 1833: 59 [unavailable generic name, synonymy by Aubé, 1838a: 406]. Trigonochilus Agassiz 1846: 377 [unjustified emendation of Trigonocheilus , unavailable generic name], 1848: 1088 [unjustified emendation of Trigonocheilus , unavailable generic name].

Porrorhynchus Laporte 1835: 108 [original description]; Guignot 1950: 124 [change in status]; Brinck 1955: 103 [change in status].

Porrhorhynchus: Régimbart 1877a: 33 [misspelling].

Porrhorrhynchus: Régimbart 1886b:250 [misspelling].

Dineutus (Porrorhynchus) : Ochs 1926: 64 [new status], 1955: 130 [change in status].

Type Species. Porrorhynchus marginatus Laporte 1835: 108 by monotypy.

Diagnosis. Medium to very large whirligig beetles; size 9–26 mm. Body form elongate-oval to teardrop-shaped ( Fig. 1 ). Antennal flagellum with 6–7 antennomeres, ultimate flagellomere trapezoidal and ca. at least 2X as long as every other flagellomere ( Fig. 2 ). Labrum large, elongate, and more or less triangular ( Fig. 1 ). Pronotum and elytra with yellow margins, often for entirety of their length, but at least in the basal half of the elytra ( Fig. 1 ). Protibia with distolateral margin spinose. Venter lightly colored.

Description. Head: Vertex and frons with punctation present, reticulation composed of round to ovoid sculpticells. Dorsal eye smaller than ventral eye, anterior margin of ventral eye situated posteriad of anterior margin of dorsal eye; orbital furrow of dorsal eye complete, becoming narrowest anteromedially; exoculata suture well-defined. Antenna with cup-like scape; pedicel broad, laterally expanded, dorsoventrally flattened, trapezoidal, lateral face with fringe of long, fine setae; flagellum with 6– 8 flagellomeres, flagellomere I stalked, triangular, ultimate flagellomere trapezoidal, at least 2X longer than flagellomeres II–V or VI, flagellomeres II–V or VI similar in size and shape. Frontal ridge length at least 1.5–2.0X width of clypeus at mid-length, frontoclypeal suture well-developed, posterior margin flat, lateral margins meeting posterior margin at ca. 100–110° angle. Clypeus weakly to fairly strongly emarginate medially, with reticulation composed of round sculpticells; punctation present, clypealium with long, fine setae ventrolaterally. Labrum large, elongate, more or less triangular, densely punctate, with reticulation composed of round sculpticells; ventral margins fringed with long, fine setae. Maxilla without galea, maxillary palp 4-segmented, ultimate palpomere about as long as proximal 3 combined, apically truncate. Labial palp 3-segmented with ultimate palpomere as long as all proximal palpomeres combined, apically truncate to subtruncate. Gula well-developed, T-shaped with tentorial pits evident, series of long, fine setae present anteriad lateral arms of gular suture. Thorax: Pronotum with punctation present, reticulation consisting of round sculpticells, lateral margins yellow with fairly broad marginal depressed area, posterolateral corners with several setae. Prosternum with well-differentiated prosternal process, prosternal process narrow and parallel-sided for entirety. Fore legs with procoxal process round to lobiform; protrochanter fusiform, posterior face with short field of curved, stout setae; profemur nearly parallel-sided for most of length, only weakly tapered apically, weakly expanded basally; protibia club-shaped with distolateral marginal apex produced to a more-or-less acute spine, anterior face with paramedial linear to arcuate series of setigerous punctures in distal half, proximal lateral margin with long groove running distal half of protibiae to distal apex with golden hairlike setae, distomedial apex encircled with short, stout, pointed setae, continuing to posterior face, ventral face of protibia with setose groove running near entire length, setae become larger, more brush-like towards distal apex, setae at distal apex projecting beyond medial process of apex; posterior face of protibia with brush of golden setae in distal 1/5; protarsus 5-segmented, ventral face of protarsomeres I–IV with long, projecting setose patch located in proximomedial corner, protarsomere V of female with short series of brush-like setae running near entire length of ventral surface; posterior surface of protarsus highly sexually dimorphic, protarsal claws similar between sexes. Elytra without sutural border, punctation present, reticulation consisting of round sculpticells, lateral margins yellow, at least basally. Mesoventrite with well-developed cavity for reception of fore leg; mesoventrite bordered anteriorly, border complete, thinly so at anteromedial projection between procoxae; projection with long setae basolaterally, large shallow punctures present anterolaterally on mesoventral body, mesoventral discrimen well-developed, running ca. 1/2 length of mesoventrite; mesepimeron narrow, strap-like. Mid-leg with mesocoxa possessing shallow, setose pit posteromedially; mesotrochanter lobiform; mesofemur broad, stout in distal half, distal apex very flatly rounded, proximal apex strongly attenuate towards trochanter; mesotibia triangular, dorsal surface with long, natatory setae, distolateral angle of dorsal surface with series of short, stout setae, distomedial surface with similar short, stout setae, adorned with 2 spines, anterior shorter than posterior; ventral face of mesotibia also with short, stout spines for entire length; mesotarsus 5-segmented, form of mesotarsomere I an equilateral triangle, 5 times length of mesotarsomere II; mesotarsomere III similar in size and form to II, all with ventral face with short, stout setae running entire length; mesotarsomere IV elongate and narrow, V ovoid with ventrodistal margin produced as spine before claws, both with long, natatory setae; mesotarsal claws larger than metatarsal claws, sexually dimorphic in shape. Metaventrite with well-developed cavity for reception of fore leg; metanepisternum lobiform; metacoxal process with posteromedial, shallow, setose pit, metacoxal process with circular pit anterolaterally, metatrochanter trapezoidal, remain- der of leg similar in form to mid-leg except metatarsal claws of both sexes smaller than mesotarsal claw. Abdomen: Abdominal tergites VI-VIII strongly pubescent with long, fine setae covering most of surface, medially darkly pigmented, lateral margins lighter yellow in color, reticulation present, composed of round sculpticells, tergite VIII with 2 types of punctation distinctly present; smaller, well-impressed punctation covering most of darkly pigmented area, second type consisting of very large, shallowly impressed crater-like punctation situated basomedially extending half its length; abdominal sternite II+III ca. 2X length of sternite IV, sternite IV ca. 2X length of sternite V, sternites V, VI, and VII similar in size, sternite VIII triangular, nearly 2X length of sternite VII, emarginate apicomedially; faintly impressed reticulation present over abdominal sternites, composed of ovoid sculpticells. Female reproductive tract with tubiform spermatheca; fertilization duct weakly differentiated; vaginal shield with anterior margin bounded by highly sclerotized bridge.

Sexual Dimorphism. Protarsus of male laterally expanded with dense covering of uniform suction cup setae occupying near entirety of posterior surface, missing only from proximomedial corner of protarsomere I. Protarsus of female not laterally expanded, without suction cup setae on posterior surface, instead posterior surface of at least protarsomeres I–IV with smaller patches of setae located at distal margins. Mesotarsal claws of male more strongly curved ventrally. Female mesotarsal claws less strongly curved, more similar in form to metatarsal claws.

Figures

Fig. 1. Porrorhynchus species, dorsal habitus. A) P. marginatus, B) P. landaisi, C) P. indicans, D) P. depressus, E) P. misoolensis. Scale bar = 5 mm.

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.