Coelostoma orbiculare (Fabricius, 1775)

Pentinsaari, Mikko, Anderson, Robert, Borowiec, Lech, Bouchard, Patrice, Brunke, Adam, Douglas, Hume, Smith, Andrew B. T. & Hebert, Paul D. N., 2019, DNA barcodes reveal 63 overlooked species of Canadian beetles (Insecta, Coleoptera), ZooKeys 894, pp. 53-150 : 53

Coelostoma orbiculare (Fabricius, 1775) Figure 1

Distribution.

Native to the Palaearctic region. Widespread and common in Europe, distributed across Eurasia to the Russian Far East and Japan ( Hansen 1987, 2004). Adventive in the Nearctic region (Ontario, Canada).

Canadian records.

Ontario: Cambridge, 01-Jun-2015 (1 ex, CBG); Hartington, 18-Apr-2017 (1 ex, CBG).

Diagnostic information

(based on Hansen 1987). Body length 4.0-4.8 mm. Habitus short and wide, convex, as in Fig. 1 . Black, with the pronotal margins sometimes narrowly red-brown. Antennae with nine antennomeres and a loosely built club with three antennomeres. Base of antennae concealed in dorsal view by the expanded lateral margin of the head. Eyes emarginate. Elytra with sharply impressed sutural striae reaching from apex at least to middle. Tarsomere 1 of meso- and metatarsi longer than tarsomere 2. Abdominal ventrite 1 without medial carina.

Bionomic notes.

This species is found in stagnant fresh water. It prefers eutrophic ponds with dense vegetation, and mainly occurs in shallow water at the edges ( Hansen 1987). One of the two Canadian specimens was collected as a larva in a leaf litter sample from a wetland, the other (an adult) was sifted from leaf litter close to a lake shore.

Comments.

This is the first record of the genus Coelostoma Brullé, 1835 in the Nearctic region. Coelostoma orbiculare leads to couplet 28 in Van Tassell’s (2001) key to North American genera of Hydrophilidae together with the genera Dactylosternum Wollaston, 1854 and Phaenonotum Sharp, 1882. It can be distinguished from Dactylosternum by the absence of a longitudinal carina on the first abdominal ventrite (present in Dactylosternum ), and from Phaenonotum by the presence of distinct sutural striae on the elytra (absent in Phaenonotum ).

Figures

Figure 1. Coelostoma orbiculare (Fabricius), habitus, L. Borowiec. Scale bar: 1.0 mm.