Oocyclus sumatrensis d’Orchymont, 1932

Short, A. E. Z. & Swanson, A. P., 2005, A revision of the Oocyclus Sharp of Thailand with description of six new species (Coleoptera: Hydrophilidae), Zootaxa 1078, pp. 1-24 : 18-19

Oocyclus sumatrensis d’Orchymont, 1932

( Figs. 5 , 14 )

Oocyclus sumatrensis d’Orchymont 1932: 685 .

Oocyclus nudus Balfour­Browne 1939: 296 . As synonym of O. sumatrensis: Hebauer & Wang 1998: 44 .

Material Examined (107). THAILAND: Phatthalung Province: Nok Rum waterfall, rock face, 37 m, 5.vi.2003, AV, Prommi & Ferro leg., L­593 (11: AEZS, UMRM). Phitsanuiok Province: Phu Hin Rongkla National Park, Namtok Romglao, 1190 m , 17.iii.2003, CMU team (1: UMRM). Satun Province: Boripat waterfall, 30.i.1995, B.J. Nichols leg., L­82 (8: AEZS, UMRM); Thanle Ban National Park, Ya Roi Waterfall, 66 m, 4.vi.2003, Sites, Vitheepradit & Ferro leg., L­592 (1: UMRM). Songkhai Province: Ton Plieuw, wet rock face of waterfall, 7.i.1995, Sites & Nichols leg., L­63 (68: AEZS, BMNH, CUIC, ISU, MCZ, NMW, UMRM, USNM); Khao Nam Chang, ca. 21 km SW of Nathawi, 13.i.1995, R. Sites & R. Nichols leg., L­72 (18: AEZS, UMRM).

Diagnosis. Posterolateral corners of pronotum angulate but not spinose ( Fig. 14 ). Procoxae covered with coarse spines. Ventrites slightly pale in coloration. Rows of setiferous punctures on elytra distinct.

Description. Size and Form. Length= 3.7–4.3 mm. EL/EW=1.07. Oval, moderately to strongly convex. Elytra slightly longer than wide. Color. Dorsum black. Head, pronotum and lateral margins of elytra sometimes with faint, mottled green to bronze iridescence, which varies in intensity and distinctness. Maxillary and labial palpi yellow. Mentum and stipes light to reddish brown, distinctly paler than ventral face of head. Epipleura, lateral margins of prosternum, and all of ventrites light brown, with remainder of venter dark brown. Basal four­fifths of femora dark brown with remainder light to reddish brown. Head. General punctation on labrum, clypeus and frons slightly variable in size from almost undetectable to fine; fairly densely distributed, distance between punctures 0.1–1.5x the width of one puncture. Systematic punctures on labrum composed of a median row of coarse punctures bearing fine, long erect setae, distance between punctures 0.5–1.5x width of one puncture. Frons with an irregular row of systematic punctures mesad of each eye, bearing fine erect setae. Clypeus with a few very indistinct systematic punctures along anterolateral margins, slightly larger than surrounding punctation and usually bearing a short seta. Antennae with scape subequal in length to segments 2–5; first two segments of club subequal in length, and apical segment slightly longer than two preceeding segments combined. Maxillary palpi short, ca. equal in length to the width of labrum; apical segment nearly twice as long as penultimate. Labial palpi three­fourths as long as width of mentum. Mentum quadrate, anterior margin slightly convex; bearing very fine and scattered punctures, some of which bear fine, long setae. Thorax. General punctation on pronotum and elytra extremely fine, nearly undetectable and generally uniform in size and distribution. Pronotal systematic punctures coarse and distinct, set with a fine recumbent seta; anterior and posterior series each forming an irregular row. Lateral margins of pronotum set with a few sparsely distributed setiferous punctures. Posterolateral corners of pronotum evenly distinctly angulate, forming a 90 degree angle, but not prolonged or spinose ( Fig. 14 ). Sutural punctation on elytra absent or unmodified from general punctation. Elytra with five diffuse rows of setiferous punctures: rows 1–3 with punctures spaced irregularly but linearly, bearing recumbent setae; row 4 more or less a field of irregularly spaced punctures with recumbent to erect setae; row 5 along extreme lateral margin, bearing erect fine setae. Prosternum with median carina along entire length, with an acute tooth anteriorly; without long spines or hairs anteriorly. Mesosternal process with lateral extensions sloping evenly downward; apex set with two long setae. Metasternum with small oval glabrous area posteromedially, about as long as wide, length of glabrous area about one­third the total length of metasternum. Procoxae covered with short, coarse spines; mesocoxae pubescent, without spines. Protibiae with 8–10 spines on dorsal face. Protarsal segments 1–4 small, subequal in length, and apical segment ca. as long as segments 1–4 combined. Abdomen. Ventrites with moderately dense pubescence, with longest setae shorter to subequal in length to longest setae around mesosternal glabrous area. Fifth ventrite entire, with pubescence slightly denser distally than ventrites 1–4. Aedeagus ( Fig. 5 ) with outer margins of parameres nearly straight in basal two­thirds; apex of parameres distinctly pointed; median lobe more or less triangular.

Distribution. China (Hainan), Indonesia (Java, Sulawesi, Sumatra), Malaysia ( Hebauer & Wang, 1998), new record for Thailand.

Remarks. Hebauer and Wang (1998) considered O. sumatrensis sumatrensis d’Orchymont to be widespread in South East Asia, and described another subspecies, O. sumatrensis tiomanensis , from Tiomanen Island, Malaysia. The exact geographic and morphological boundaries separating these two subspecies is unclear. The Thailand specimens we have examined agree more closely in external characters and male genitalia with O. sumatrensis tiomanensis , although this subspecies was considered endemic to Tiomanen Island. However, until the status of these two subspecies can be re­evaluated, we refrain from assigning subspecific rank to these specimens.

Figures

FIGURES 1 – 6. Oocyclus aedeagi, dorsal views. 1. O. viridescens sp. n. 2. O. sitesi sp. n. (holotype). 3. O. namtok sp. n. 4. O. thailensis sp. n. (holotype). 5. O. sumatrensis d’Orchymont (specimen from Thailand). 6. O. melinoventris sp. n. Scale Bar = 0.18 mm.

FIGURES 11 – 15. Details of Oocyclus. 11 – 12. Thoracic sterna. 11. O. melinoventris sp. n. (holotype). 12. O. sitesi sp. n. (holotype). 13 – 15. Lateral margin of pronotum, with posterolateral corner to the right. 13. O. viridescens sp. n. 14. O. sumatrensis d’Orchymont. 15. O. thailensis sp. n. Scale bar = 1 mm.