Brown scale (Parthenolecanium corni) insects on a stem of a greenhouse-grown grapevine (Vitis vinifera). The picture shows a row of scales attached to the stem; the largest is about 8mm long. The scales have been present throughout the previous growing season, causing the formation of a groove in the bark. Each is a shell containing a mature female insect. She builds the shell when she settles to feed on the plant's sap. Within the scale, she produces a waxy secretion into which are laid up to 2000 eggs. Scale insects are members of the order Hemiptera. Eggs hatch into nymphs. They leave the scale and feed on foliage during the summer, returning to overwinter on stems and branches. Scale insects are difficult to eradicate due to the close adherence of the scale to its substrate, and also to the wax within it. Females reproduce parthenogenetically; males are short lived and rarely seen.