Dragons.

These terrifying and stunningly beautiful things are the nymphs of the Banded Demoiselle (the damsel fly with the lovely blue spots on the wing of the male). They joyously turned up in the Riverfly sampling I did last night on the Little Avon in Gloucestershire.
What also turned up were Gammarus (an excellent bellwether of water quality), ephemera nymphs, heptagenidea, fish fry, leeches, snails, worms, eels etc etc etc.
This little, loved and cared-for stream is in rude health. That makes me very happy indeed.