The evolutionary stability of mutualisms is enhanced when partners possess mechanisms to prevent overexploitation by one another. In obligate pollination-seed consumption mutualisms, selective abortion of flowers containing excessive eggs represents one such mechanism, but empirical tests have long been limited to the yucca-yucca moth mutualism. We present evidence for selective abortion in the recently discovered mutualism between Glochidion trees and Epicephala moths. In Glochidion acuminatum, proportion of aborted flowers progressively increased both with higher egg load and increased ovule damage. Selective abortion resulted in a 16% seed production increase compared with expectations under random abortion, and moths suffered fitness losses as high as 62% when ovipositing into pre-infested flowers. Moth eggs were laid singly more often than expected under random oviposition, thus avoiding potential disadvantages from multiple infestations. As new pollination mutualisms are being discovered, selective abortion mechanisms may prove to be more widespread than previously thought. © 2010 Blackwell Publishing Ltd/CNRS.