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Merchant Grain Beetles

Once considered to be the same as a saw-toothed grain beetles, merchant grain beetles have since beetles found to be a separate species.  A worldwide pest, the merchant grain beetle has adapted to cooler climates.  Adults are capable of flight, approximately 1/8 of an inch in length, dark brown in color and displaying the six saw-like teeth along the segment directly behind the head.  Merchant grain beetles are known for being attracted to light sources.  Females lay an average of 22-190 white, shiny eggs in a single manner or in small clusters in crevices of food material over a period of several months.  Eggs hatch within a few days.  Mature larvae are yellow to white in color, less than 1/8 of an inch in length and are elongated in shape.  Three other species of beetle larvae share this same description.  Larvae molt three times prior to construction of their pupal cell or cocoon which is constructed of food particles and held in place by sticky oral secretions.  With a life cycle from egg to egg of 30-40 days, an average of 6-7 generations per year occurs.  When conditions are not favorable, development may require more than a year to complete.  Adults typically live for several months.  Merchant grain beetles are not capable of attacking whole kernels; however, their flattened bodies allow them to slip into packages through small gaps and packaging imperfections.

As with a majority of stored product pests, thorough inspection to determine infested areas and products is a must with merchant grain beetles.  Common products for infestation include: nuts, cereal, rolled oats, rice flour, cake mixes, macaroni, cookies, coconut, puffed rice and candy bars that contain peanuts.  Infested products will need to be destroyed or removed.  Upholding high levels of sanitary control will also assist in limiting activity.  Application of a residual insecticide by a pest control professional should be completed after cleanout of infested products and resolution of unsanitary conditions.