The elongate orange eggs are arranged in clusters of 10 or more, usually on the undersides of host plant leaves. Eggs hatch in about a week. Small, dark grubs emerge and develop rapidly into orange or red humpbacked, full-grown grubs or larvae. The larvae have two rows of dark spots along the sides of their bodies. There are four larval grub stages, which take about 2 to 3 weeks for completion.
Adults emerge in a week or two.
These mate and lay eggs for the second brood. In Washington there are two generations per year. Although chiefly a pest on potatoes and sometimes on tomatoes, these beetles can survive on cabbage, eggplant, and many weeds when potatoes are not available. Extensive feeding on the leaves and stem tips can prevent tuber development in potatoes, or fruit development on other host plants and, therefore, reduce yields. When the first adults emerge in the spring, potato plants have not yet broken through the ground.