The utility of the cosmopolitan scuttle fly, Megaselia scalaris (Loew, 1866) (Diptera: Phoridae), as a biological control agent of the litter-dwelling darkling beetle Luprops tristis (Fabricius, 1801) (Coleoptera: Tenebrionidae), a serious home-invading pest of southern India, is reported. In the laboratory, M. scalaris parasitized dormant, aggregated populations of L. tristis. Megaselia scalaris completed its life cycle by feeding on the decaying substrate consisting of dead L. tristis and their excreta. Megaselia scalaris larvae fed on the viscera of parasitized L. tristis within a day and were not deterred by the defensive gland secretion of the host. The scuttle fly preferred L. tristis as a food source even when an alternative organic food source was available, and it parasitized only inactive L. tristis. Our results are contrary to the presently existing conclusion that facultative parasitism by M. scalaris in laboratory cultures of target organisms makes it unsuitable as a biological control agent of L. tristis.