Potamanthus luteus
Potamanthus luteus is a species of hacklegilled burrower mayfly in the family Potamanthidae. According to Fauna Europaea it is found over a range of mainland Europe. In the UK it is or was found principally on the Rivers Usk and Wye in the UK; in the Usk it may have become extinct and in the Wye it has suffered a population crash.