"Sminthurides aquaticus" or "Sminthurides bifidus" from Bristol Botanic Gardens, Bristol, England, United Kingdom. "Original description on Flickr:" :"Female dark colour form Sminthurides aquaticus sensu Shaw 2013 + tentatively Sminthurides bifidus sensu Janssens 2013" :"Went back yesterday to Bristol Botanic Gardens to take samples and took some more photos, especially of this dark form which is rather splendid."