While on and excellent FSC course at Flatford Mill I caught a burrowing mayfly nymph Ephemera sp. It is the nymph of the original Mayfly,
which are most commonly on the wing in May, hence the name which is named after the Mayflower, better known as hawthorn, which blooms at the end of April when the mayfly emerges (thanks to Craig Macadam @bugsymac1 for the correction!). The nymphs live in burrows in the mud or sand at the bottom of ponds, lake and slow flowing rivers. This one was placed in my photographic aquarium and I filmed it twice as it burrowed into the fine gravel.
You can see its gills (along the sides of its abdomen) beating, which is how they keep a flow of oxygen rich water through their burrow. I write more about these guys another time.