Hydrobius fuscipes

Using both Hackston and Duff keys this is usually quite a straightforward beetle to identify. However it seems that things have become more complicated as the species is now split into three: fuscipes, rottenburgii and subrotundatus. All of the older records below, certainly those up at least 2022 (and 2023?), were identified as fuscipes using one or other key and without knowledge of the split. I don't know how to tell rottenbergii but it's supposed to live in coastal rock pools so none of mine (all from inland locations) are likely to be that, and until 2026 the only information I had about subrotundatus is that it used to be regarded as a variety of fuscipes and as such, Duff describes it as a "shorter and more convex form with darker legs." There is some variation among my photos in how dark the legs appear, though I suspect that has as much to do with how the photos were taken as it does with actual darkness of the legs. For now my working assumption is that they're all fuscipes. It's by far the most frequent member of the family to be attracted to light round here.

Recently (early 2026) I realised that the Beetles of Europe website (coleonet.de) covers the seperation of these three species, so hopefully from now onwards I will be able to confirm whether or not they all are indeed fuscipes or not.

Hydrobius fuscipes, North Elmham (Norfolk, UK), 30th July 2022

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 29th June 2025

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 16th July 2024

Hydrobius fuscipes, North Elmham (Norfolk, UK), 27th August 2024

Hydrobius fuscipes, North Elmham (Norfolk, UK), 29th June 2023

Hydrobius fuscipes, North Elmham (Norfolk, UK), 31st July 2024

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 26th June 2023

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 17th September 2024

4x Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 9th August 2023

Hydrobius fuscipes, North Elmham (Norfolk, UK), 11th July 2023

Hydrobius fuscipes, North Elmham (Norfolk, UK), 12th August 2024

2x Hydrobius fuscipes, Hoe Rough (Norfolk, UK), 23rd July 2023

2x Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 20th August 2021

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 23rd August 2024

Hydrobius fuscipes, North Elmham Cathedral Meadows (Norfolk, UK), 11th June 2018

Hydrobius fuscipes, North Elmham (Norfolk, UK), 10th August 2023

Hydrobius fuscipes, North Elmham Cathedral Meadows (Norfolk, UK), 10th July 2021

Hydrobius fuscipes, North Elmham Cathedral Meadows (Norfolk, UK), 19th August 2018

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 2nd August 2021

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 25th September 2021

Hydrobius fuscipes, Wendling Beck Project (Norfolk, UK), 18th August 2024

Hydrobius fuscipes, North Elmham (Norfolk, UK), 9th September 2021

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 10th August 2020

Hydrobius fuscipes, North Elmham (Norfolk, UK), 10th July 2022

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 14th July 2018

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 23rd June 2023

Hydrobius fuscipes, North Elmham (Norfolk, UK), 17th July 2020

Hydrobius fuscipes, North Elmham (Norfolk, UK), 19th July 2018

Hydrobius fuscipes, North Elmham (Norfolk, UK), 20th July 2018

Hydrobius fuscipes showing close-up of scutellum, Wendling Beck Project (Norfolk, UK), 6th July 2023

Hydrobius fuscipes, North Elmham (Norfolk, UK), 21st July 2018

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 23rd July 2018

2x Hydrobius fuscipes, North Elmham (Norfolk, UK), 26th July 2018

Hydrobius fuscipes, North Elmham (Norfolk, UK), 8th July 2018

Hydrobius fuscipes, North Elmham (Norfolk, UK), 2nd August 2018

Hydrobius fuscipes, North Elmham (Norfolk, UK), 16th July 2022

Hydrobius fuscipes, North Elmham (Norfolk, UK), 5th August 2024