T. nigrescens feeds primarily on the larger grain borer but can survive for long periods of time without the borer or any food at all, except for limited amounts of vegetable matter. The beetle is attracted to the borer by smells or pheromones, then kills it both in and out of grain stores.
Discovery of the beetle resulted from work done by GTZ, the German Agency for Technical Cooperation. GTZ scientists have been looking for a way to biologically control the larger grain borer since 1984. When they compared borer habitats in Costa Rica and Africa, they discovered the beetle predator which is not found in Africa.