Ypsiloncyphon

Zwick, Peter, 2014, Australian Marsh Beetles (Coleoptera: Scirtidae). 6. Genera Calvarium Pic, Papuacyphon Zwick, and Ypsiloncyphon Klausnitzer, Zootaxa 3846 (1), pp. 1-41 : 16-19

Ypsiloncyphon , species group 3

Description. Small (BL 1.44–2.32mm), oval to elongate and parallel-sided, moderately convex sexually dimorphic beetles. Females are more slender than males ( Figs. 50–52 ). Colour of dorsal surface blackish, antennae and legs yellowish. Males of Y. bicolor with bright red head and pronotum. Punctures on head and scutellum (very fine) and pronotum (much coarser) raised, granular, concave punctures on elytra often larger than those on forebody. Pilosity fine, semi-erect, greyish, often giving specimens a dusty appearance, in particular females.

Head small, eyes protruding. The oral area occupies about 1/3 of total head width. Antenna: scape globular, no sharp edge. Pedicel stout but smaller than scape. Segment 3 much thinner but not much shorter than pedicel. Flagellum loosely articulated, individual segments simple, elongate, the last with blunt apex ( Fig. 53 ).

Labrum short, transverse, sides rounded, front margin almost straight. Mandibles symmetrical, the sharp slender pointed apex bent mediad, no tooth, molar region smooth, microtrichia along mesal edge visible only at 400x ( Fig. 54 ). Maxillary and labial palpus with thick penultimate segment on which the small nipple-like last segment inserts terminally ( Figs. 55–56 ).

Pronotum extended a little towards scutellum, indistinctly truncate in front of it, posterior edge laterally slightly sinuous ( Figs. 51, 52 ). Convex pronotal sides converging forward, front angles blunt but well marked and a little projecting because the front edge is shallowly concave. Scutellum an equilateral triangle with very fine granular punctures. Elytra without ribs or folds, irregularly punctate. Both sexes fully winged.

Ventral face. The long gular sutures end before reaching the bay-like area where the maxilla articulates (fig. 5 in Zwick 2013b). The subgenal ridge continues dorsad alongside the mouthparts, to the inside of the antennal foramen. Eventually, the ridge forms the supraantennal ridge and runs laterally towards the eye. No buttonhole configuration.

Prosternal process drop-shaped, receiving groove of corresponding shape, shallow, anteriorly wide, sides diverge forward, rear end rounded. In Y. longus n. sp., a slender species, the process is elongate, in the stouter Y. virgulifer n. sp. it is broadly drop-shaped.

Process of mesoventrite caudally widened, trapezium-shaped, reaching back to the front of the metaventrite which does not extend forward between the middle coxae. Discrimen of metaventrite complete ( Fig. 57 ). Abdominal sternites 3–7 exposed, unmodified, no hair tufts.

Male. T8 with stout, short, divergent, caudally unconnected apodemes (e.g., Figs. 62, 75, 90). Plate with microtrichia, caudal margin additionally with some short setae (mostly not shown in figures). T9 with long unconnected apodemes, plate soft, hairless, no defined shape (e.g., Figs. 63, 76, 100). S9 longer than T9, capulus handle-like, plate deeply divided, either into closely appressed straight rods ( Fig. 58 ), or two unequal slightly divergent flat blades (e.g., Figs. 64, 79). The longer blade of S9 is on the left hand side of the body (e.g., Figs. 64, 79, 102). In preserved specimens it sometimes projects from the body, its tip is therefore occasionally broken. Penis with long handle-like pala, long flat trigonium and even longer parameroids (e.g., Figs. 77, 93, 118). The trigonium is basally rigid, it cannot be bent as a whole but the caudal section beyond a constriction is often bent ventrad (e.g., Figs. 60 , 122 ). The extreme tip is more strongly sclerotized than the rest of the trigonium. Anterior plate of the pala asymmetrical, the line that can be drawn through the bases of the parameroids, across the trigonium, is slightly oblique with regard to the long axis of the penis. Penis distally symmetrical. Tegmen and parameres about as long as the penis, in the form of long narrow struts in symmetrical Y-shaped arrangement, the unpaired base of variable length.

Female. S7 of several species with a median nipple-shaped outgrowth which at rest is not exposed but folded forward under segment 8 (not figured). Female of Y. katherinae n. sp. with paramedian notches on the caudal edge of T7 ( Fig. 107 ). Apodemes of S8 anteriorly connected, either forming an anteromedian sclerite rod so that the entire S8 resembles the letter Y, or a tuning fork (e.g., Figs. 68, 81, 106), or a wide loop with sclerotized flanges along its sides (e.g., Figs. 119 , 124 , 132 ). Apodemes of T8 long, those of ovipositor even longer. Gonocoxites and stylites slender, with elongate apical sensilla, not distinctive. Female genitalia include an elaborate vulvar sclerite inside the ovipositor, but no prehensor. The large vulvar sclerite consists essentially of paired elongate sclerites dorsally connected by a transverse sclerite bridge. Details vary with species, extreme morphs resemble boxes (e.g., Figs. 82, 128), others tubes (e.g., Fig. 124 ). Gonoduct near bursella armed with many small cuticular discs (bursellar pores: Libonatti & Ruta 2013). Both sides of the bursella armed with a cuticular network, the dictyon (Greek, a net) which is composed of connected cells and resembles a honeycomb, or a plate formed of large bubbles (e.g., Fig. 120 ). The two sclerites are congruent, the cells closest to the accessory gland are largest. Peripheral projections make some cells resemble cogwheels (e.g., Figs. 109 , 120 ).

Notes and etymology. The symmetrical toothless mandibles, the non-projecting front corners of pronotum, the narrow parallel-sided mesepimeron, and apodemes of male T9 much longer than those of T8 are shared with other species of Ypsiloncyphon . The shape of the mesoventral process varies in the genus (from SEM micrographs; courtesy of R. Ruta), with a tendency for caudal enlargement. In Y. species group 3 the caudal width of the process is extreme.

Pronounced sexual dimorphism occurs among various Scirtidae . Examples in the Australian fauna include, e.g., Petrocyphon Watts, 2011 (some males with prolonged antennae: Watts 2011, Zwick 2013a), Chameloscyphon Watts, 2011 and Pachycyphon Zwick, 2013 (wingless females: Watts 2011, Zwick 2013b). The slenderness of females of Y. species group 3 is striking.

Identification of females seems sometimes easier than of males. However, females of the earliest named species, Y. micans , are not definitely known. Therefore, I designate male types for the new species. Unless differently stated all species agree with the general description above, only diagnostic details are mentioned in the individual descriptions which are presented in the order in which they appear in the key to males. Descriptions of some informally named females are appended.

Figures

FIGURES 50 – 52. Ypsiloncyphon longus, n. sp., sexual dimorphism: 50, plot of body width (BW) against body length (BL); 51, male, 52, female, habitus to the same size, not to scale.

FIGURES 53 – 57. Ypsiloncyphon longus, n. sp., antenna, mouthparts, and thoracic structure: 53, antenna; 54, left mandible; 55, left maxilla; 56, labium; 57, ventral face of meso- and metathorax, after a cleared slide mount, semi-diagrammatic. Freely visible sclerites identified by grey shade. Abbreviations: Cx 2, Cx 3, middle, hind coxa; d: discrimen; F 2: femur 2; mem: mesepimeron; mes: mesepisternum; msp: mesoventral process; mtp: metaventral process; mv: metaventrite; Tr 2: trochanter 2. Pilosity diagrammatic. All mouthparts to the same scale, other figures not to scale.

FIGURES 58 – 61. Ypsiloncyphon virgulifer, n. sp., male: 58, T 8, T 9 and S 9, superimposed; 59, penis, ventral view; 60, oblique dorsolateral view of same, trigonium tip bent ventrad; 61, tegmen and parameres. Pilosity and surface structure of T 8 and T 9 shown only diagrammatically in small selected areas. All to same scale.

FIGURES 121 – 126. Ypsiloncyphon angustus, n. sp.: 121, male S 9; 122, penis, dorsolateral (near Herberton); 123, penis, dorsal (Big Mitchell Ck); 124, female terminal segments with vulvar sclerite, apodemes of S 8 black, expansions grey (Rocky Ck); 125, female, tip of T 7; 126, dictyon. Figs. 121 – 123 to the same scale, 125 not to scale.

FIGURES 103 – 109. Ypsiloncyphon katherinae, n. sp., male (103 – 105) and female (106 – 109): 103, ♂ holotype, S 9; 104, penis, dorsal; 105, tegmen and parameres; 106, ♀ (N of Tennant Ck.) terminal segments, apodemes of S 8 black; 107, ♀ T 7; 108, vulvar sclerite; 109, dictyon. Figs. 103 – 106 to the same scale.

FIGURES 117 – 120. Ypsiloncyphon brevis, n. sp.: 117, male S 9; 118, penis, dorsal (Sth. Pine R.); 119, female terminal segments with vulvar sclerite, apodemes of S 8 black, expansions grey (Goldmine & Davies Cks); 120, dictyon. All to the same to scale.

FIGURES 129 – 133. Ypsiloncyphon sp. B (129 – 131; from near King Cascade) and Y. sp. C (132, 133); 129, female terminal segments, with vulvar sclerite in situ; apodemes of S 8 black; 130, dictyon; 131, vulvar sclerite, enlarged, not to scale. 132, female segment 8, apodemes of S 8 black, flange grey; 133, vulvar sclerite. 129 & 130, and 132 & 133 to the same scale, respectively.