An ecological study in southern Cameroon explored the relationships between arthropods and the trash-basket epiphytic fern, Platycerium stemaria (P. Beauv.) Desv. (Polypodiaceae). Arthropods shelter in cavities situated among the tangled roots of the fern or between them and the bark of the host trees, or they develop in the compost and hanging soil that form from vegetal debris trapped by the barren fronds. This fauna provides the fern with nutrients. Large numbers of detritivorous arthropods accelerate the remineralization of the vegetal debris trapped by the fronds, improving the quality of the compost that feeds the epiphyte. Ant fauna is relatively diverse because of the presence of opportunistic species; particularly predators specialized in the capture of arthropod taxa that feed on the debris trapped by P. stemaria. On the other hand, P. stemaria mostly shelters three ant species in cavities limited to the tangle roots and so can be considered a myrmecophytic epiphyte. The nitrogen-rich wastes of ant colonies likely improve the quality of the compost that feeds the fern. Platycerium stemaria presents therefore similarities with certain neotropical bromeliads.