Adult females of Eretmocerus eremicus and Encarsia formosa, aphelinid parasitoids of Bemisia tabaci and Trialeurodes vaporariorum, are known to feed on honeydew and hemolymph of both whitefly hosts. Because these easily accessible food sources contain different sugars, we selected glucose, sucrose and fructose as host-honeydew sugars and trehalose and glucose as host-hemolymph sugars and determined the effects of these four sugars on parasitoid longevity in the laboratory. Each of the four sugars increased the female longevity of both parasitoids, and for Er. eremicus, there was no significant difference in longevity among the four sugars, but for En. formosa, trehalose had a significantly smaller positive impact on longevity than the other three sugars. We conclude that glucose, fructose and sucrose in the host honeydew and glucose in the host hemolymph greatly increase the female longevity of both parasitoids. We also conclude that Er. eremicus can also utilize trehalose fully in extending female longevity, while En. formosa can not. This suggests that host hemolymph containing trehalose is more important as a carbohydrate source for Er. eremicus than for En. formosa.