Mexican Bean Beetles

Photo Credit - Purdue University

The Mexican bean beetle is quite voracious and can decimate your beans in a couple of days.

Mexican bean beetle (MBB) larvae and adults feed on the underside of leaves between the veins, removing the lower epidermis of the leaf.

More info:

http://entnemdept.ufl.edu/creatures/veg/bean/mexican_bean_beetle.htm

Pictures:

https://www.google.com