Scanning electron micrograph of a feeding peach/potato aphid, Myzus persicae. The picture shows the tip of the rostrum (brown), a sheath corresponding to the mandibles and maxilla of biting insects. It protects the stylet (yellow); a flexible tube about 3 microns in diameter, 100x thinner than a hypodermic needle. Feeding involves probing a leaf prior to inserting the stylet, lubicrated with saliva to ease its penetration. The aphid feeds from phloem cells (for sugar) and xylem (for water to regulate its osmotic pressure). If the leaf is virus infected, virus may be transferred via the stylet to the next plant visited. M persicae infests many plant species, including crops. It is economically important as a vector in the spread of virus diseases, including beet western yellow virus, BMYV, in both sugar beet and winter oilseed rape; beet mosaic virus, BMV, and potato virus Y, PVY