The map is based on records from NBN Gateway, with yellow dots showing pre 1990 records, reds dots 1990 – 2015 records and red on yellow dots overlapping records. Aquarius paludum does nor occur in Ireland.
Aquarius paludum (14 – 16 mm) and Aquarius najas (13 – 17 mm) can be distinguished from all other skaters found in the UK by size, with the exception of Limnoporus rufoscutellatus (13 – 17 mm), a species established in Ireland but a rare vagrant in England, which has a reddish centre to the pronotum.
A. paludum is characterised by long abdominal spines that are angled upward and reach the tip of the abdomen, and by a yellow line along the side of the pronotum. A. najas has shorter spines and no yellow line.
Abdominal spines Yellow line along the side of the pronotum