The adult weevil is dark gray and white speckled and 14 to 15 millimeters long.

The eggs are deposited one by one in notches the female digs into the root crown of the knapweed.

The larva emerges from the egg and tunnels into the root cortex where it feeds on the plant tissue.

It is established in much of the western United States and there is evidence that it reduces knapweed biomass.

Cyphocleonus achates was released to the Hiawatha National Forest in Michigan's Upper Peninsula in summer 2009.