Found at Ed Garden: Mexican Bean Beetle

On Monday 7/26/10 a Master Gardener Volunteer found these cute-ugly creatures that look like a nib of moldy corn. 

"What are these?"  She asked, turning over the leaf of a bush bean.  

"I will find out!" I declared.

It is the pupa of the Mexican  Bean Beetle. 

The Mexican bean beetle is actually a cousin of the ladybird beetle, one of the few destructive species of this primarily beneficial family of insects. The adult is oval shaped and copper colored, with 16 black spots on its back. It is about 5/16 inch long and 1/4 inch wide. Females lay yellow, oval-shaped eggs in clusters on the underside of bean leaves. From these eggs, hatch yellow larvae with branched spines that cover their soft bodies. There are 4 larval stages, the final one reaching a length of 1/3 inch, before transforming into a bright yellow pupae. The pupae are usually found attached to the underside of leaves.

 The best way for us to control these beetles is simply to pick them off by hand and toss them into a bucket of soapy water.  Or, if you like, squish them between your fingers!