Sieve-tube sap from the petioles of Heracleum Mantegazzianum and Picea abies stems was obtained by severing the proboscides of aphids tapping the sieve tubes of these plants. Sucrose was the only sugar detected in the sieve-tube sap, and occurred at concentrations of 24% (Heracleum) and 10% (w/v) (Picea). Volumes of sieve-tube sap equal to 5500 sieve-tube cells of Heracleum and 50 sievetube cells of Picea exuded from severed aphid probiscides.

The mouth-parts of the aphids living within hollow Heracleum petioles normally penetrate the xylem of the vascular bundles in order to reach the phloem sieve-tubes. The aphids also tap the sievetubes of isolated phloem strands.