Visual Reference Library - Insects

Prostephanus truncatus 
Length: Approx. 3- 4.5 mm
A dark brown beetle with a cylindrical body shape, when viewed from above the rear of the insect is square shaped. The thorax bears rows of teeth on its upper front edge and the head is turned down underneath the thorax so that it cannot be seen from above.
The larger grain borer usually is restricted to corn (maize) and does not commonly occur north of Mexico. The insect is larger and darker in color than the lesser grain borer.
The larger grain borer is a serious pest of stored maize and will attack maize on the cob, both before and after harvest. Adults bore into the maize husks, cobs or grain, making neat round holes and tunneling extensively producing large quantities of grain dust as they tunnel. The adults prefer grain on cobs to shelled grain.

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Last updated December 2016