The influence of aphid-produced honeydew on parasitoid fitness and nutritional state: A comparative study

•The carbohydrate content and longevity of Lysiphlebus testaceipes differed greatly when it fed on 14 different honeydews.•There was not a significant effect of aphid or host plant phylogeny on the quality of honeydew for parasitoids.•There was a positive correlation between the body sugar content of honeydew-fed parasitoids and their longevity.•Sugar content of honeydew-fed parasitoids gives information on their fitness, independently of the sugar source they fed on.