This is another of the sedge-mining Elachista species, utilising Lesser Pond-sedge Carex acutiformis, Greater Tussock-sedge (C. paniculata) and Bladder-sedge (C. vesicaria), and can be found in wet bogs and acid heath. It is widespread but local throughout the UK.
The larval mine appears from March to May. It is a short mine occupying half the blade’s width, often situated halfway between the tip and the base.
The larva is yellowish green or grey, with a brown or black head and a light brown prothoracic plate.
Pupation is under a girdle in the angle of a leaf, with emergence from May to early August. The species can be bivoltine in the extreme south-west of England.
Dissection is recommended to separate the adult from the very similar Elachista albidella and Elachista eleochariella.