We analyzed the effect of predation and parasitism by the native dryinid <span name="style_italic">Haplogonatopus hernandezae</span> as a natural enemy of the rice pest <span name="style_italic">Tagosodes orizicolus</span> under controlled conditions in an insectary in Costa Rica. We found no change in the proportion of <span name="style_italic">T. orizicolus </span>nymphs that were fed upon, parasitized, and that showed no apparent damage throughout the adult stage in <span name="style_italic">H. hernandezae</span>, which favors a stable control of the pest. The percentage of <span name="style_italic">T. orizicolus</span> nymphs that were parasitized (37 %) and preyed upon (36.5 %) was similar, eliminating 73,5 % of the total nymphs causing damage to the rice plants (N = 1 099). Of the total 324 parasitized nymphs, female nymphs were more parasitized than male nymphs (95 % and 5 % respectively) and dryinids developed more successfully in female host nymphs. These tendencies did not change with dryinid age. Survival of dryinids was higher in female <span name="style_italic">T. orizicolus</span>, both for larvae that emerged from the host and pupated, and for pupae that moulted to adults. In cages where the nymphs had no contact with dryinids we found a higher amount of males than females (57.44 ± 28.5 vs 45.22 ± 25.85). In contrast, when the nymphs were in contact with dryinids, the sex ratio was two females to one male reaching adulthood since the dryinids fed more on male nymphs (N = 692). Our results indicate that female dryinids prefer to oviposit in female <span name="style_italic">T. orizicolus </span>nymphs and prey on males. Reproduction by parthenogenesis, acceleration of the development in an insectary with controlled conditions and eficiency of <span name="style_italic">H. hernandezae </span>as a parasitoid and predator<span name="style_italic"> </span>indicate that this dryinid is an effective biological control agent of <span name="style_italic">T. orizicolus</span>. Rev. Biol. Trop. 57 (Suppl. 1): 203-211. Epub 2009 November 30.. Rev. Biol. Trop. 57 (Suppl. 1): 203-211. Epub 2009 November 30.

rice; biological control; Homoptera; Haplogonatopus hernandezae; parasitoid; Tagosodes orizicolus; Costa Rica