Pollen and nectar are the most important floral rewards in plant—pollinator interactions. These rewards are voraciously consumed by hummingbird flower mites (Acari: Mesostigmata: Ascidae), and nectar and pollen feeding by mites have a strong impact on plant—hummingbird interactions. Tropicoseius chiriquensis (Acari: Mesostigmata: Ascidae) feed on nectar and pollen of Lobelia laxiflora H.B.K. (Lobeliaceae) flowers, and within the floral corolla they mate and lay eggs. Yet the benefits of nectar and pollen feeding in terms of survival and fecundity of flower mites are quite unexplored. Here, we evaluate the fecundity and numerical response of T. chiriquensis to the availability of pollen in long-lived protandrous flowers of L. laxiflora. Under field conditions, unmanipulated flowers with pollen had more mites (adults, nymphs, larvae, and eggs) than emasculated flowers without pollen, Numbers of mites fluctuated throughout the flower life span. More adult mites were found for the first 2 d of the flower (staminate phase) and decreased for the last three days of life of the flower (pistillate phase). In contrast, we found higher number of larvae in the pistillate phase. In a laboratory experiment, the fecundity of flower mites was 4 times as high when pollen was available as that when flower mites were not provided with pollen. They completed their life cycle in approximately a week, the life span of L. laxiflora flowers. Our results suggest that pollen availability in L. laxiflora long-lived flowers could influence the population dynamics of T. chiriquensis by having a positive impact on numbers and fecundity of the mites.