We describe and illustrate the life history and immature stages of Anthonomus monostigma Champion (Curculionidae: Curculioninae: Anthonomini). This weevil is a fruit borer in Miconia calvescens DC (Melastomataceae), a Neotropical tree that is invasive in Pacific islands. The larva has three instars, and development from egg to adult requires approximately two months. In Costa Rica, A. monostigma larvae were found in three Miconia species, and adults fed only on Miconia species. Host relationships of the A. monostigma group suggest that this group could be related to the A. partiarius and A. albocivitensis groups (sensu Clark 1992, 1993b). The potential of A. monostigma as a biological control agent is discussed.