Small beetle ID

[Lord V]

Small beetle about 2.6mm body length on a compost bin lid, taken Yesterday.
Any ideas on ID ?

Thanks
Brian v.

[healfdan]

I am fairly certain this is an aquatic beetle...possibly Helophorus aquaticus

[Paul mabbott]

A lovely little thing and certainly a Helophorus sp.. I don't know the genus that well and have enough problems with them under the microscope; there are several common species.
Although the former family Helophoridae is now generally included in the Hydrophilidae ("Water Beetles") they might better be called "mud beetles" being found on the muddy edges of ponds, in puddled damp patches and not uncommonly in cattle dung.

[Matt Smith]

Helophorus aquaticus was a name that used to be applied to what are now 2 separate species, H.grandis and H.aequalis.

From the size its not H.grandis or H.aequalis, and the slightly uneven shape of the last segment of the palp indicates it is not H.brevipalpis. Any better ID almost certainly requires a look under the microscope and probably a dissection of a male specimen to get a good det.

[Lord V]

Thanks for the tentative ID's. I found it on top of the compost bin lid but the compost is certainly rather damp and interestingly I do dump sludge from my pond filters into the compost bin as well as algae and leaves from the pond.
Brian v.