Coelostoma (s. str.) vividum Orchymont, 1936

Sheth, Sayali D., Ghate, Hemant V. & Fikáček, Martin, 2020, Review of Coelostoma of the Indian subcontinent (Coleoptera: Hydrophilidae) Part 1: Coelostoma s. str. and Holocoelostoma, European Journal of Taxonomy 690, pp. 1-32 : 19-21

Coelostoma (s. str.) vividum Orchymont, 1936

Fig. 8 A–K

Coelostoma vividum Orchymont, 1936: 28 .

Coelostoma (s. str.) vividum – Jia et al. 2017: 118 (faunistics).

Differential diagnosis

Coelostoma vividum is easy to recognize due to its small body size and the aedeagus with the apically strongly narrowed median lobe.

Material examined

Paratype

INDONESIA • 1 ♂; “Bengealis” [Bengkalis]; [1º25ʹ38.96ʺ N, 101º36ʹ45.94ʺ E]; [40 m a.s.l.]; 1885; Maindron leg.; IRSNB .

Other material

INDIA – Assam • 1 ♂, 2 specs; “ Kohora (= Kaziranga village), Green Reed Hotel ; 27º35.93N 93º26E ” [26º35ʹ21.81ʺ N, 93º24ʹ44.07ʺ E]; [1000 m a.s.l.]; 16–18 Apr. 2008; Fikáček, Podskalská and Šípek leg.; at light; NMPC . – Meghalaya • 1 ♂, 6 specs; W Garo Hills, Bagmara ; 25º11.5 N, 90º38.5 E; ca 100 m a.s.l.; 15–21 May 1996; Jendek and Šauša leg.; NHMW .

BANGLADESH • 1 ♂; Dinajpur; [25º37ʹ40.48ʺ N, 88º37ʹ59.43ʺ E]; [41 m a.s.l.]; Oct. 1969; Barbe leg.; NMPC .

Published records

PAKISTAN: Khyber Pakhtunkhwa: Madyan ( Jia et al. 2017). NEPAL: Mahakali distr., Kanchanpur Mahendranagar ( Jia et al. 2017). INDIA: West Bengal: ‘Bengalʼ (Orchymont 1936), Kolkata (Orchymont 1936).

Description

FORM AND COLOUR. Body length 3.4–4.1 mm, body width 2.1–2.3 mm. Body oval in dorsal view, moderately convex in lateral view. Head black; pronotum and elytra uniformly black to dark brown with slightly paler margins; ventral surface uniformly dark brown. Tarsi pale brown. Mouthparts and antennae yellowish, antennal club brown.

HEAD. Dorsal punctation dense, consisting of coarse simple punctures, a few punctures with associated ridges in posterior-most region; trichobothria present; surface between punctures smooth. Anterior margin of clypeus gently arcuate. Eyes large, interocular distance ca 4.0× the width of one eye in dorsal view; eye emarginate anteriorly. Labrum moderately sclerotized, largely exposed anterior of clypeus, pale brown in coloration. Antenna with 9 antennomeres, club loosely segmented. Second maxillary palpomere moderately broad.

PROTHORAX. Pronotum bisinuate anteriorly, anterolateral corners obtuse; posterior margin moderately bisinuate, posterolateral corners rectangular. Lateral margin with very indistinct sculpture; anterior and lateral margins with distinct bead not extending to posterior margin. Pronotal punctation sparser and finer than on head, consisting of simple punctures without associated ridges; surface between punctures smooth. Prosternum straight on anterior margin, carinate mesally, anterior portion of carina raised, producing tooth-like process seen in lateral view.

MESOTHORAX. Elytral punctation dense and moderately coarse, consisting of punctures without transverse ridges. Series of punctures absent. Sutural stria impressed, present in apical half. Mesoventral plate 1.1× as long as wide, arrowhead-shaped, bluntly pointed anteriorly, posteriorly widely attached to metaventrite.

METATHORAX. Metaventrite raised medially, surface glabrous with sparse regular setae; lateral portions densely pubescent. Anterior metaventral process narrowly projecting between mesocoxae; posterior process bifid. Wings well-developed (macropterous).

LEGS. Profemur with dense pubescence except in apical fifth; mesofemur with sparsely arranged stout setae only; metafemur with sparse pubescence.

ABDOMEN. All ventrites densely pubescent. First ventrite without carina. Posterior margin of last ventrite entire, without stout spines mesally.

AEDEAGUS ( Fig. 8 J–K). 0.6 mm long. Median lobe triangular, broad at base, tapering towards narrowly spatulate apex; gonopore situated basally, widely semicircular. Parameres slightly longer than median lobe; broad, weakly pointed at apex, inner margin with setae. Phallobase small, slightly wider than long.

Biology

Unknown. Published specimens were all collected at light.

Distribution

Widespread species, so far recorded from northern Pakistan ( Jia et al. 2017), Nepal ( Jia et al. 2017), India (Orchymont 1936; this paper), Bangladesh (this paper), Cambodia ( Jia et al. 2017), southern China ( Jia et al. 2017) and Indonesia (Java, Sumatra, Borneo; Orchymont 1936).

Figures

Fig. 8. Coelostoma (s. str.) vividum Orchymont, 1936, specimens from Assam: Kohora (NMPC). A. Dorsal habitus. B. Lateral habitus. C. Frontal view. D. Thorax in ventral view. E. Dorsal punctation of head. F. Dorsal punctation of pronotum. G. Dorsal punctation of elytron. H. Abdominal ventrites. I. Detail of abdominal apex. J–K. Aedeagus: dorsal (J) and ventral (K).