The Mexican bean beetle is an extremely destructive pest. They start out as fuzzy yellow larvae, commonly seen on beans and peas. The adult beetle is one third inch or less in length and yellow to copper in color with 16 black spots on the back. At first glance this appears to be just another friendly little lady bug, but don't be fooled. The beetle rapidly attacks many varieties of bean and pea plants, turning the plant into nothing but a skeleton.
Photo shows the two damaging stages of the beetle.
The adult beetle has 16 black spots on its yellow-brown wing covers. The larvae are spiny yellow grubs. The adult beetles hibernate in protected places. They first appear on bean plants during April and May when they lay yellowish eggs in large clusters on the leaves. The yellow larvae hatching therefrom feed and pupate on the plants from which the newly emerged, light lemon-colored adults appear.