Elachista tetragonella

Elachista tetragonella is a moth of the family Elachistidae. It is found from Fennoscandia to Spain and Italy and from France to Bulgaria.

The wingspan is 6 - 7 mm. Adults are on wing in January and again in June.

The larvae feed on Carex montana. They mine the leaves of their host plant. The mine has the form of a white elongate gallery in the top region of the leaf. The frass is deposited irregularly. Pupation takes place outside of the mine. They are dirty yellow with a pair of grey dorsal length lines and a yellowish head. Larvae can be found from April to the end of May.