Gyrinus urinator Illiger, 1807

This quaintly named beetle is a mostly southern European species which also occurs across North Africa and the Atlantic islands, to the north it extends to the UK and various Baltic countries but is absent from Denmark and Fennoscandia and otherwise sporadic and generally rare e.g. it has recently been discovered in Germany after an absence of fifty years and its presence in Poland needs recent confirmation. Here it occurs throughout England and Wales although the distribution is predominantly southern and eastern and there are very few recent records from Wales and northern England, it is widespread though scarce and very local in Ireland and there is a single Scottish record from Islay. Modern records suggest an increase in abundance and range but for many areas e.g. most of Wales, it is known only from older records. On the continent adults have been recorded from both fresh and brackish water, generally in lowland streams and stagnant ponds exposed to the sun, although they have been recorded up to 1200m in the Atlas Mountains. In the UK the usual habitat is slow-moving rivers and canals, sometimes in marginal situations shaded by trees etc but they may also occur in other habitats e.g. we found them in Surrey gyrating on a sparsely-vegetated heathland pond fully exposed to the sun. Adults occur year-round; they may be observed gyrating on the surface, sometimes in company with G. substriatus Stephens, 1828, but are more often found by sweeping among marginal vegetation or searching floating logs and debris, especially in cooler periods and during the winter.

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Adults are easily identified, even in the field; they are one of only two UK species with the ventral surface entirely pale, the other being G. minutus Fabricius, 1798 which is smaller, 3.5-4.5mm, and has a distinctive keel on the scutellum. A large, 4.8-7.8mm, and broadly-oval species very similar in size and shape to G. substriatus but easily distinguished by the elytral colouration which consists of longitudinal stripes of metallic bronze and black. Dorsal surface shiny black with a bronze lustre to the lateral margins and metallic bronze margins to the elytral striae, microsculpture extremely fine and only visible at high magnifications, about X150. Mesosternum with a longitudinal impression only in the basal half, in G. minutus it is complete to the anterior margin between the front coxae. Inner elytral striae much weaker than the outer striae, sometimes almost missing, arcuate series of punctures before the apex strong and well-impressed, lateral border wide to just before the outer apical angle where it narrows to the apical margin.