A phloem-sap feeder mixes phloem and xylem sap to regulate osmotic potential

► Phloem-sap feeders have to overcome high phloem sap osmotic pressure. ► We tested the hypothesis that xylem sap consumption contributes to osmoregulation. ► Aphids consume more xylem sap after three different osmolality-increasing treatments. ► Xylem sap consumption is a general response to osmotic stress.