Information on the value of various food types for harvestmen is sparse. The aim of this study was, therefore, to clarify the quality of six different food types to a harvestman. Survival, growth and development were used as measures of fitness in a laboratory experiment. Recently hatched Oligolophus tridens were fed the following experimental diets until maturity: Drosophila melanogaster (Diptera), entomobryid Collembola (Tomocerus bidentatus/Sinella curviseta), Folsomia candida (Collembola), Sitobion avenae (Aphidoidea), Rhopalosiphum padi (Aphidoidea), and a mixed diet containing the five prey types. Survival and growth rate were high on the D. melanogaster and entomobryid diets, and low on the F. candida, S. avenae and R. padi diets. The mixed diet caused a high early mortality, later a good survival and a high growth rate. The majority of harvestmen on the D. melanogaster and entomobryid diets matured. None of the harvestmen fed pure aphid diets developed beyond the fourth instar, and only few from the F. candida diet matured. Overall, the diets separate in three levels: D. melanogaster and the entomobryid diet were high-quality, the mixed diet was intermediate, and the two aphid diets and F. candida diet were low-quality. In general, the quality ranking agrees with that of other generalist predators, though there are differences in details.