MERCHANT GRAIN BEETLE INFORMATION & FACTS

The merchant grain beetle, Oryzaephilus Mercator (Fauvel), is a stored product pest found worldwide.  They are most commonly found in home pantries, warehouses, mills, grain elevators, and in railroad cars and cargo ships which transport food items from place to place.

Merchant grain beetles favour nuts, seeds and products with a higher oil content like processed cereals, oat grain and bran, and will also attack and infest processed flour, rice, macaroni, cookies, dried fruits and even some types of chocolate bars. Their flat bodies can pass through packages with tiny tears in their seals.

Adult merchant grain beetles resemble the sawtoothed grain beetle.  They are brown, 1/8” long, with a flattened body and 6 saw-like teeth on each side of its prothorax. The merchant grain beetle can be distinguished by the shape of its head which is square-shaped. At maturity, it has fully functional wings, and can fly. They are attracted to light.

Image source: CSIRO

The life cycle of a merchant grain beetles has 4 stages - egg, larval, pupal, and adult. The timing from egg to adult is dependent on heat and humidity, and can be as short at 2 months. Females deposit their eggs (40-300 per year) within or around stored products. Within 10 days the larvae hatch, feed and can transform into mature adult beetles just months later. Depending on their habitat, adult merchant grain beetles can live from 6 months to 3 years. 

Learn more about how to get rid of pantry pests.