Platyparadonus Etzler and Ivie

Etzler, Frank E. & Ivie, Michael A., 2019, Platyparadonus, A New Circum-Caribbean Genus Of Sand-Associated Negastriinae (Coleoptera: Elateridae), Proceedings of the Entomological Society of Washington 121 (1), pp. 15-25 : 17-22

Platyparadonus Etzler and Ivie , new genus

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Type species: Platyparadonus marleyi Etzler and Ivie , new species.

Diagnosis.— Platyparadonus appears to be closely related to other Negastriinae genera that lack visible elytral striae, such as Paradonus Stibick ( Fig. 5 ) and genera placed in the tribe Quasimusini Schimmel and Tarnawski 2009 ( Fig. 6 ). Both Paradonus and Platyparadonus can be separated from the genera of Quasimusini by lacking hind angles that embrace the humeral angles of the elytra (see key above). Platyparadonus can be distinguished from Paradonus by the following combination of characters: lateral carina of pronotum limited to pronotal hind angle ( Fig. 14 ), antennae passing posterior edge of pronotum by 3.5-4 antennomeres, antennomere 2 onethird longer than antennomere 3 ( Fig. 9 ), and possessing laterally lobed tarsomeres (bilobed or cordiform, Fig. 16 ). Species of Paradonus possess a complete lateral carina on the pronotum; antennae that do not pass the posterior edge of the pronotum; antennomere 2 slightly longer than, but almost equal in length to, antennomere 3; and tarsi simple, with filiform tarsomeres.

Description.—Body length 2.3–3.6 mm. Body uniform, yellow-brown to dark brown. Body dorso-ventrally flattened ( Fig. 2 ).

Head ( Figs 10–12 ): punctures indistinct, small, simple, deep, separated by one to two diameters of punctures, interspaces rough and densely microreticulate, setae short, dense, yellow to grey; eyes semicircular, truncate dorsally, not bulging; supra-antennal carina short, merging with clypeal margin so frons not separate from clypeal margin; mouthparts prognathous, mandibles tridentate ( Fig. 8 ), maxilla as in Fig. 7 . Antennae ( Fig. 9 ) feebly serrate, sometimes almost filiform; passing posterior edge of pronotum by 3.5–4 antennomeres; antennomere 1 (pedicel) expanded, curved and smooth posteriorly, densely setose anteriorly; antennomere 2 cylindrical, as long as 1; antennomere 3 feebly serrate, about two-thirds length of 2; antennomeres 4–10 feebly serrate, all subequal in length to one another; antennomere 11 oval, with single dorsal impression; antennomeres 4–11 with apical third often subtly lighter in color, each bearing a black spot near ventral side near midlength or apical two-thirds; setae erect; punctation on antennomeres 1–3 similar, subtly less than punctation on antennomeres 4–11.

Thorax: pronotum ( Figs. 13–15 ) wider than long, widest at mid-length, sides broadly arcuate, lateral carina limited to pronotal hind angle only, posterior edge with ‘m’-shaped notch just anterior of scutellum, sublateral basal incisures not present; hind angles short, sharply pointed, not extending past posterior edge of pronotum, not embracing humeral angle of elytra, hind angle lacking dorsal carina; punctation large, lacking patterned placement but uniform (no difference between disc and lateral area), subumbilicate, adjacent to separated by 2X diameter of a puncture, interspaces dull, densely microreticulate. Hypomeron not separated from pronotum by carina, dull, appearing rough, interspaces densely microreticulate, punctures only visible along prosternal suture, separated by a diameter at most, hind angle visible, but not strongly projecting posteriorly, small medial projection behind procoxal cavity present. Prosternum broad, widest near anterior third, punctures large, lacking patterned placement but uniform throughout, subumbilicate, some nearly touching to separated by a diameter of a puncture, interspaces dull and microreticulate, carinate around procoxal cavities; anterior lobe short, rectangular, truncate to slightly convex medially, not covering ventral mouthparts, not deflexed ventrally, two black spots on either side of midline present basally (not visible in most noncleared specimens); prosternal sutures curved, marginate along hypomeral border, shining, not excavate or grooved anteriorly; prosternal process straight, slender, acutely pointed, very short past procoxae, without lateral expansions, flattened between procoxae. Mesosternal fossa shallow, parallel sided, not angled ( Fig. 19 ). Mesepisternum and mesepimeron fused, not reaching mesocoxal cavity, mesocoxae surrounded by meso- and metaventrite, meso- and metaventrite fused medially. Metaventrite with deep, simple punctation, separated by 0.5X diameter medially, rapidly becoming sparser laterally, separated by 1.0 diameter or more, punctures not easily distinguished from interspaces, interspaces microreticulate and dull. Scutellar shield ( Fig. 18 ) subpentagonal, weakly convex, about 2X longer than wide, anterior edge slightly curved, carinate and elevated above base, posterior edge broadly rounded, surface minutely punctured and weakly shining. Elytron ( Fig. 17 ) with single stria near scutellar shield and 2X length of scutellar shield, otherwise lacking dorsal striae, punctures small, subumbilicate, separated by 1–2X diameters, apical fifth lacking punctures, interspaces microreticulate, dull, obscuring punctation, ventral striae (only visible ventrally or in cleared specimens) absent medio-basally. Legs ( Figs. 16, 20 ) yellow-brown, femora enlarged and laterally flattened, tibiae moderately laterally flattened, metatibia more so, expanded distally, bearing a single apical spine, tarsomeres dorsoventrally flattened, bilobed (cordiform), all approximately equal in length, less pronounced bilobes on metatarsi, which are relatively longer compared to pro- and mesotarsi, claws simple, without basal setae, strongly curved; metacoxal plate ( Fig. 20 ) with ventral expansion as wide as base until midlength, then rounded at 90-degree angle, extremely narrow at lateral margin.

Hind wing (Fig. 24): well developed, 2.3X as long as wide; wing membrane notched in anal area. Radial cell reduced, 2.1X as long as wide, proximal, posterior angle obtuse; horizontal radial crossvein (r3) extending from radial cell 1.8X length of radius; radial vein thickened apically, with slight posterior projection at apex. Vein MP 4 without apparent crossvein to CuA 2. Wedge cell absent. Apex of wing membrane without venation, occupying 0.33X length of wing membrane, with two weakly sclerotized areas. Posterior membrane edge with setal fringe. Abdomen: punctures small, not separable from interspaces, which are microreticulate and dull. Fifth abdominal ventrite broadly rounded posteriorly. Terminal ventrite either wide, broadly rounded apically (females, Fig. 22 ), or narrow, hour-glass shaped, rounded apically (males, Fig. 23 ). Terminal tergite similar to female terminal ventrite in both sexes.

Male genitalia ( Figs. 25–29 ): Aedeagus equal to half length of abdomen to as long as abdomen, straight or possessing slight dorsal curve basally. Parameres with basal portions (basimere) fused to one another and medio-ventral strut of median lobe, forming rigid cylinder, dorsum covering ventrum side except near base; gradually attenuate basally, apex moderately rounded to subacute; apical portions (telomere) slender, separated dorsally as a movable condylite with digitate base and articulate to medio-ventral strut of median lobe, bearing one major subapical seta, apex narrowly rounded; full paramere complex subparallel throughout. Median lobe (centerpiece) broad, lateral struts slightly arcuate at base, otherwise straight, not reaching paramere base, apex usually moderately acuminate, exceeding apex of parameres. Basal piece small, weakly sclerotized, subquadrate.

Female genitalia ( Fig. 21 ): ovipositor weakly sclerotized, 0.8X length of abdomen. Coxites setose, lacking styli. Paraprocts elongate, 0.6X length of ovipositor. Uterus membraneous, without sclerotizations, bulbous; colleterial glands not visible, bursa copulatrix connected to uterus by narrow tube, divided into two membraneous arms [these arms may be the spermathecal gland].

Etymology.—The name Platyparadonus is the combination of Platy -, derived from the Greek word platus meaning broad or flat, referring to the dorso-ventrally flatted aspect, and Paradonus to denote a possible relationship with species in the genus Paradonus . The name is masculine in gender.

Notes.—The known distribution of Platyparadonus is circum-Caribbean, known from the Greater Antillean islands delimiting the Caribbean to the north and the north coast of South America to the south. It would not be surprising if species were to be discovered along the Caribbean coast of Central America and in the Lesser Antilles, even the Lucayan Archipelago.

Specimens were collected by sifting beach wrack or at an ultraviolet light. All localities seem to be on or near marine sand beaches. Their presence under beach wrack and the dense (hydrofuge?) setae on the body may suggest that they are able to float to the surface if their substrate is flooded. More detailed habitat data are presented under each species.

Only two species are known in the genus. Species descriptions that follow are short, highlighting unique aspects of each species, otherwise both species share the characters given in the genus description.

Figures

Figs. 1–6. Habitus photos, lines each equal 1mm. 1, Dorsal habitus, Platyparadonus marleyi, Holotype. 2, Lateral habitus, P. marleyi, Holotype. 3, Ventral habitus, P. marleyi, Paratype, female, Jamaica. 4, Dorsal habitus, Platyparadonus beckeri, Holotype. 5, Dorsal habitus, Paradonus obliquatulus (Melsheimer, 1845), USA. 6, Dorsal habitus, Quasimus sp., Malaysia.

Figs. 7–23. Morphological characters. All figures on same scale. Line on left is 1mm. All are P. marleyi, unless noted otherwise. 7, Right maxilla, dorsal view. 8, Right mandible, dorsal view. 9, Left antenna, dorsal view, setae not illustrated. 10, Head, dorsal view. Punctures and most setae not illustrated. 11, Head, lateral view. 12, Head, ventral view. 13, Pronotum, dorsal view. Punctures and setae not illustrated. 14, Pronotum, three-quarter lateral view. 15, Pronotum, ventral view. 16, Right proleg. Some setae not illustrated. 17, Right elytron. Punctures (open circles) not visible dorsally. Dotted Pattern to illustrate microreticulation. 18, Scutellum. 19, Mesoventrite. 20, Right metaleg. Setae not illustrated. 21, Ovipositor and internal female genitalia. bc = bursa copulatrix (?), u = uterus, v = vagina. 22, Terminal ventrite, female. Usually not visible. 23, Terminal ventrite, male, P. beckeri. Usually not visible.

Figs. 25–29. Hind wing and aedeagi. Lines below wing and left of aedeagi are 1mm. All aedeagi on same scale. 24, Right hind wing, P. marleyi, dorsal view. 25, P. marleyi, dorsal view. 26, P. marleyi, lateral view. 27, P. marleyi, ventral view. 28, P. beckeri, dorsal view. 29, P. beckeri, ventral view.