Wing span 8 - 9mm.
A very local species (Nationally Scarce A), restricted to the edges of saltmarshes, brackish ponds and ditches in coastal areas from Hampshire to Suffolk.
It is single-brooded, the adults on the wing in June and July and the larvae mining the leaves of Sea Club-rush (Bulboschoenus maritimus).
This is the smallest of the Monochroa species with grey, rather plain forewings and a single black discal spot. Dissection is usually required to rule out the superficially similar species M. hornigi and M. arundinetella.
One of very few British species that has a scientific name derived from a biblical source (from Moses, "drawn out of the water", as the mine-bearing leaves are).