A new species of the recently revised genus Parosus is described, P. amayae López-García Marín-Gómez sp. nov., from adult and larval specimens collected in bracts of Columnea medicinalis in the Natural Reserve Río Ñambí (Southwestern Colombia). Observations on the interaction with the plant, subsocial behavior, and population density are presented and discussed. Adults and larvae apparently live together and feed on eggs and larvae of flies that develop inside the decomposing fruits of C. medicinalis. The new species is illustrated by color habitus photos, as well as its L1 and L3 larvae, male and female genitalia are depicted by line drawings.