Blackfly Larvae

Blackfly Larvae

Observation - Blackfly Larvae - UK and Ireland. Description: Keep finding lots of these larvae in my river samples but not sure what they are. They tend to stick to the bottom of the tray and float around in the current.Any ideas?

Keep finding lots of these larvae in my river samples but not sure what they are. They tend to stick to the bottom of the tray and float around in the current.Any ideas?