Hyphydrus ovatus (Linnaeus, 1761)

A generally common species throughout England and Wales including Anglesea and Man although there are far fewer records north of south Yorkshire and Lancashire. In Scotland there are scattered, mostly west coastal, records north to Glasgow and Edinburgh. Their normal habitat is stagnant still water and temporary ponds, drainage channels and slow moving water rich in detritus and vegetation. They are found throughout the Watford area, sometimes in small and shallow bodies of water e.g. the pond on Bushey Hall golf course (TQ125985), sometimes among samples from the rivers Gade and Colne, and they are present throughout the extensive drainage channels below Cassiobury park to Cassiobridge. Further afield they occur in suitable habitats along the Colne valley from Watford south to Cowley (the extent of our sampling). Sieving samples of bottom mud and debris from around marginal vegetation will often produce them, in our experience the adults occur as single specimens or as male/female pairs. Eggs are laid singly on the leaves of submerged vegetation during May and June, and possibly later, and the tiny larvae hatch within a few days. Soft, newly emerged adults have been recorded in September (Balfour-Browne), they hibernate but despite a great deal of local sampling around ponds known to host the species we have yet to find them during the winter. Locally we have recorded adults during July, August and September.

The small globular form and dark red colouration are distinctive and, once familiar, the species will not be confused with any other
4-5mm. Form globose, ferrugineus, elytra darker or with paler lateral margins and base. Antennae testaceous, all segments elongate. Palpi testaceous. Head densely punctate and with fine isodiametric microsculpture. Eyes large, front margin of clypeus raised and weakly bordered. With two weak depressions on vertex at level of hind margins of eyes. Pronotum with strongly protruding front angles, hind margin sinuate and lateral edges bordered, without lateral or basal furrows. Densely punctate in male, these punctures varying in size and confluent basally, cuticle finely reticulate and shining. Puncturation sparse in female, punctures smaller and disc almost impunctate, entire surface densely reticulate and dull. Scutellum not visible. Elytra distinctly angled with pronotum when viewed from above, very finely pubescent and with apex rounded. Puncturation dense in male, with larger and smaller punctures which are sometimes longitudinally confluent along basal margin. Cuticle shining with faint reticulation. Female elytral puncturation fine and sparse, reticulation very dense so elytra dull. Nilsson and Holmen (1995) state that some females have shiny elytra. Underside and legs testaceous. Front and middle tarsi apparently four segmented, fourth very small, third strongly bilobed. Segments 1-3 with fine median longitudinal furrow. Segments 1-3 dilated in male. Middle and hind tibiae and tarsi with fine long swimming hairs above. Hind tibiae with two strong apical spurs, the inner of which is larger. Five segments of hind tarsi obvious.

A second species, H.aubei Gang., from the Channel Islands is given in Friday and separated on colour: yellow-red with black markings. This is not included in the latest (2008) Coleopterist checklist.

Description from 2 Watford specimens at X40

Nilsson, A.N. and Holmen, M. 1995. The aquatic Adephaga of Fennoscandia and Denmark 2:Dytiscidae (Fauna Ent Scand 32)