Description of a new species, Stactobia pacatoria sp. n., from Lebanon, clearly belonging to the nielseni-group, as defined by Schmid (1959). Notes are given on the 5th instar larva and the pupa, as well as on the remarkable larval and pupal cases, which are built using minute calcite fragments abundantly present in the biotope of the species (a madicolous habitat with very hard water).