Developmental time and fecundity of Aphidius colemani Viereck and Aphidoletes aphidimyza Rondani were studied under laboratory conditions on cucumber plants infested with Aphis gossypii Glover at a constant temperature of 20 degree C, photoperiod of 18 hours and 70% R. H. Developmental time from egg to adult for A. colemani lasted 13.9 days and for A. aphidimyza, from egg to larva was 3 days, larva to pupa 5.8 days, from pupa to adult 11.9 days, and total developmental time was 20.6 days. The average lifetime fecundity was 57.7 for A. colemani and 55.07 for A. aphidimyza. The variation for both species was considerable. Percentage of females for A. colemani was 58% and for A. aphidimyza 66%. One larva of A. aphidimyza will, on average, kill 23.8 A. gossypii during its life. Predation of parasitized aphids by A. aphidimyza was observed. Production of parasitoids was lower when the predator was present. The use of the two natural enemies together in control programs against A. gossypii is discussed. missing