Flour Beetle

The mealworm beetle, also known as the yellow mealworm, is a common household pest, especially in pantries and kitchens. The adult female lays tiny eggs in grain containers, so homeowners often do not notice the problem at first. The larval stage is the most visible, growing to about an inch long, and can be found in grains, cereal products and decaying plant and animal matter. Pet shops also raise mealworms as food for reptiles and turtles, and they are used as fishing bait. Here is what you need to know about this beetle and how to deal with it.

What Does a Mealworm Beetle Look Like?

Adult mealworm beetles are shiny, dark brown to black and about 12–15 mm long. The larvae are yellowish, start out small and grow up to about 30 mm long, with a hard outer shell. They feed on damp or moldy grain, meat, dead insects, dried fruit, oats, flour, ground foods and other starchy products commonly found in homes, and some also feed on decaying plants.

Why Do Mealworm Beetles Come Indoors?

Mealworm beetles prefer dark, damp places such as grain stores and homes where boxes and packages of cereal are kept. They enter homes in search of food and shelter, and females like to lay their eggs in grain containers and food cupboards, which makes homes an ideal place for them to feed and breed.

Mealworm Beetle Life Cycle

Females lay around 500 eggs, and they breed continuously and in large numbers. The eggs hatch within about two weeks, and the larval stage lasts around three months before the insects mature and mate. The beetle passes through four stages (egg, larva, pupa and adult), and the whole cycle can take anywhere from four months to a year, depending on temperature and food availability.

• Larva: Larvae, known as mealworms, appear right after the eggs hatch. They are white at first, with a slender, segmented body, and turn yellowish-brown within a few days, feeding on the surrounding food until they reach about an inch long.
• Pupa: The larva turns into a C-shaped, yellowish pupa that darkens as it approaches adulthood.
• Adult: In summer, the adult emerges from the pupa. It is white or orange at first, then darkens to black, with a hard shell. Adults move slowly, can fly, and live for 3 to 12 months.

What Damage Do Mealworm Beetles Cause?

Finding mealworms in stored food is unpleasant, and the larvae contaminate grains and other products, which can cause digestive problems if eaten. Long-term infestations can trigger allergic reactions such as headaches and asthma, and the droppings, shed skins and other debris they leave behind make food unfit to eat. Their presence is also a sign of poor storage conditions.

How to Prevent Mealworm Beetles

• Store food in dry areas, in sealed containers.
• Check stored food products regularly.
• Inspect old, ground or moldy foods.
• Throw away spoiled or infested food products.
• Keep your home, floors and cupboards clean.

Because mealworm beetles breed so quickly, an infestation can become serious in a short time and often requires professional treatment. For a lasting solution, Safeguard’s beetle control experts can identify the species, find the source of the infestation and design a treatment program that fits your home and budget.