During the summer of 2011 a Malaisetrap was set up along a brackish ditch in the Jeronimuspolder in Sint-Laureins to make an inventory of invertebrates. On the banks of the ditch a lot of Scirpus maritimus L. grows and a salty meadow is bordering the ditch. A total of 150 species were identified, belonging to 18 insect and 5 spider families. Seven species are halophilous or halobiont, comprising Stratiomyidae (two species), Dolichopodidae (three species), Muscidae (one species) and Cicadellidae (one species). Four other species are not true halophilous, but tolerate high salt concentrations. Amongst the non-halophilous species there are habitat specialists of reed vegetations, marshes and oligotrophic grasslands. Therefore it is important to maintain the patchwork of micro(habitats) for the conservation of the invertebrate diversity in the studied area. The Malaise trap sampling provided the first observation in Belgium for two Muscidae : Helina maculipennis and Coenosia antennata , the latter being halophilous. Another species, the halophilous Cicadellidae Paramesus obtusifrons , was recorded in 2011 for the first time in Belgium and is now known from the Jeronimuspolder and from four other Belgian localities.