RESUMO
The predatory stink bugs are well known by their behavior, but the knowledge of the immature morphology and their natural history are scarce. Studies on predatory stink bugs are important to better understand their evolution and their use as biological controllers. Here, we describe the morphology of egg and the five nymphal instars of Oplomus catena (Drury, 1782), using optical and scanning electron microscopy. In general, O. catena immatures are very distinctive from other Asopinae species already studied. The egg is black, with short aero-micropylar processes and similar to those described for Stiretrus species. The nymphs can be diagnosed by the abdominal plates very large and bright blue. The color polymorphism of adults is fully illustrated, and four color patterns are proposed. The natural history of the species is described based on field and laboratory observations. The known prey of the species is reviewed and new preys are reported. The morphological and biological traits here described are discussed in order to better understand the biological role of predatory stink bugs.