none Aphidius colemani; Aphidius matricariae; HEMIPTERAN-HOSTS; Aphis gossypii; Potential biological control agent evaluation Aphidius; Ephedrus cerasicola; Lysiphlebus testaceipes; CONTROL-OF; Aphis gossypii (Hemiptera); Potential control agent evaluation; HEMIPTERAN-HOSTS; Aphis gossypii; Potential biological control agent evaluation Aphis gossypii; CONTROL-BY; Braconidae (Hymenoptera); Potential control agent evaluation; HYMENOPTERAN-PARASITES; Braconidae; Potential biological control agent evaluation Four aphidiine parasitoid species (Hymenoptera: Braconidae) were evaluated with respect to their potential to control Aphis gossypii Glover (Homoptera: Aphididae) in glasshouse cucumbers. In a laboratory experiment thirty cotton aphids were offered to individual females for two hours. Aphidius matricariae Haliday parasitized less than six percent of the aphids and was ruled out as potential biological control agent. Ephedrus cerasicola Stary and Lysiphlebus testaceipes Cresson parasitized 23 and 26 percent of the aphids, respectively. Aphidius colemani Viereck parasitized 72 to 80 percent of the aphids. With the latter three species, experiments were performed in small glasshouses with cucumbers (Cucumis sativus L. cv. 'Aramon'). As in the laboratory test A. colemani performed best; significantly more colonies were found and parasitization rates in the colonies were higher by A. colemani than by E. cerasicola and L. testaceipes. Because of the good correspondence between laboratory and glasshouse experiments, it is suggested that bad performance of an aphid parasitoid species in a simple laboratory trial might be sufficient evidence to disregard this species for further tests.