The syrphid subfamily Microdontinae is characterized by myrmecophily of their immature stages, i.e., they develop in ant nests. Data on natural history of microdontines are scarce, especially in the Neotropics. Based on fieldwork in southern Brazil, this study provided new data on development and ecology of the hoverfly Pseudomicrodon biluminiferus (Hull) (Diptera: Syrphidae) as well as the first morphological descriptions of male genitalia, larvae, and pupa. Immature specimens were specifically found in colonies of the ant species Crematogaster limata Smith (Hymenoptera: Formicidae) found in rosettes of the bromeliad species Aechmea lindenii (E. Morren) Baker (Poales: Bromeliaceae) and A. nudicaulis (L.) Grisebach. Third instar larvae were observed preying on ant larvae, revealing the parasitic nature of P. biluminiferus. In this and several other aspects, the natural history of P. biluminiferus is similar to that of Holarctic microdontine species. Exceptions include: (i) indications that adults of P. biluminiferus outlast the winter months (in contrast to 3^rd instar larvae in Holarctic species) and (ii) P. biluminiferus' relationship with bromeliads. The importance of bromeliads for this host-parasite system is evaluated in this paper. The single occurrence of another, unidentified microdontine species' pupae in a nest of the ant species Camponotus melanoticus Emery (Hymenoptera: Formicidae) is reported.