Ilybius ater

Some references use a vernacular name for this species: Mud-dweller.

The majority of these were identified using Mike Hackston's keys (I might have used Duff for the most recent one).

Ilybius ater, North Elmham Cathedral Meadows (Norfolk, UK), 10th July 2021

Ilybius ater, North Elmham (Norfolk, UK), 21st July 2017

Ilybius ater, Thompson Water (Norfolk, UK), 19th March 2017

Ilybius ater, North Elmham (Norfolk, UK), 14th August 2017

Ilybius ater, North Elmham (Norfolk, UK), 14th August 2018

Ilybius ater, Hoe Rough (Norfolk, UK), 23rd July 2023

Ilybius ater, Wendling Beck Environment Project (Norfolk, UK), 9th August 2023

Ilybius ater, Wendling Beck Environment Project (Norfolk, UK), 25th June 2025

This pair were caught together (at light) but when keying them I measured the male to be marginally below the minimum length of Ilybius ater. I was pretty sure it was nevertheless ater as I could see no difference in the mattness of the elytra, but keyed it through as smaller just in case. I hit a dead-end at Ilybius quadriguttatus as size suggested that species but the absence of a clear ventral tooth on the front tarsal claw meant it couldn't be that.

male and female Ilybius ater showing hind tarsal claws of the male, Wendling Beck Environment Project (Norfolk, UK), 11th August 2025