ABSTRACT: Certain biological aspects of the Staphylinid predator, Philonthus longicornisSteph. (Coleoptera: Staphylinidae) had been studies when preyed on many insect larvae (e.g. Diptera, Coleoptera and Lepidoptera), however these studies on snails and slugs are few. So, the present work was studied the biological parameters of P. longicornis preying on the terrestrial snail, Monacha obstructa Pfeiffer (Stylommatophora: Hygromiidae) under laboratory conditions. Duration of mature and immature stages and preying capacity of M. obstructa were investigated at degree of temperature (20±1°C) combined with relative humidity (70±5%). At these conditions, tallest oviposition periods, highest number of eggs laid, lowest percentages of mortalities and highest preying capacity were recorded.