Grain Borer

Prostephanus truncatus

Appearance

• Brown body colour. 1/16" to 3/16" in length.
• Antennae have 3 large segments at the end forming visible antenna clubs, reddish in colour.
• The humped thorax covers the head, its front rim has teeth–like indentations.
• Elytra (wing covers) are heavily punctated and drop off sharply at the back, giving the impression of a square end when seen from above.

Lifecycle

• The female lays an average of 10 eggs on a grain of maize and the hatched larvae bore into the grain.
• The larva undergoes up to 4 development phases and pupates inside the corn grain.
• Lifecycles can be quite short, in good conditions (25 days at 34 °C, 75% relative humidity) there are several generations per year.

Habits

• Adult beetle is a pest of stored maize, but also infests other types of grain.
• Larva bores tubular passages into the grain, typically making one main tunnel with smaller ones branching off.
• Brought in from tropical Central America in cassava roots and tapioca products, as well as in starchy fruits and tubers.