Bean leaf beetles are ab out 1/5" in length. They are typically yellow in color but may also be red or tan and have a black triangular marking between their wings. They also typically have 4 black spots on their wing covers, although these are not always present.
Bean leaf beetles feed on foliage, potentially resulting in significant defoliation. This defoliation is most damaging to yield at bloom. Later in the season they also feed on pods, resulting in direct yield losses.
Insecticides are available for controlling bean leaf beetles. The number of beetles present and the extent of defoliation, along with the ability of the plant to recover, should be considered when deciding if treatment is necessary. Always read and follow all label instructions.