Yellow Mealworms

Facts, Identification & Control

Scientific Name

Tenebrio molitor


What do they look like?

Mealworm image licensed under CC

Yellow mealworm adults look like typical beetles, and are not worm-like in appearance as their common name suggests. They are dark in color, have a hard shell and are about ½ inch long.


The common name mealworm comes from the appearance of the larvae (caterpillars), which are cylinder-shaped and about an inch long when full grown. Their coloration is yellow with brownish rings on the body segments. The larval body turns progressively harder as they grow.

How Did I Get Yellow Mealworms?

Homeowners often find yellow mealworms in neglected areas of homes prone to humidity. Forgotten bagged or boxed items in kitchen pantries are hotspots for these pests. Yellow mealworms are common wherever stored food becomes damp or grows mold. Mealworm larvae are one of the largest insect larvae that infests stored products since the full grown mealworm larvae is about 1 inch long.

A female yellow mealworm will lay eggs in grain products, so tainted bags of flour can start an infestation. Garden or bird seed left in outbuildings also attract the pests.

How Serious Are Yellow Mealworms?

Yellow mealworm infestations are usually a sign of poor sanitation. The pests contaminate all products they eat, which leads to costly food losses. Residents who accidently ingest yellow mealworms may have some gastric discomfort, but the pests do not transmit diseases.

Getting Rid of Mealworms

How Orkin Treats for Mealworms

Mealworms are stored product pests that primarily feed on damp, decomposing and moldy grain-based products that become. Outdoors, they feed on items such as grain in bins, leaves, dead insects and animal wastes. Their normal habitat is dark, cool, moist locations where there is suitable food, shelter and moisture. Mealworms may not be noticed until they are seen inside and begin infesting grain products in storage areas.

When mealworms are seen, the first thing the homeowner should do is contact their pest management professional and request an inspection. During the inspection, your pest management professional will correctly identify the pest, locate where they are living and determine how to apply an integrated mealworm treatment program to solve the problem.

The mealworm treatment program prepared by your pest management professional may include:

  • Provide useful information related to mealworm habits, habitats, behavior and treatment options to customers.
  • Sanitation recommendations that focus on removing the mealworm’s sources of food and shelter. Sometimes the source of the mealworm problem is old grain-based products like rodent baits that may have been left after the homeowner has used them to control rodents. Using a vacuum or other equipment to clean up and remove old baits, infested food products and perhaps an infested bird nest in attics may sometimes be all that is needed for mealworm treatment.
  • Other times, however, the treatment plan may require applying a product to the exterior and/or interior of the house to help control the mealworm population. Your pest management professional’s experience and knowledge is needed to ensure that products are used in accordance with the product’s label directions

Behavior, Diet, Habitats

Diet: What Do Mealworms Eat?

Mealworms are categorized as secondary stored product pest. This means they primarily feed on materials that are damp, decomposing and moldy. Their preferred food sources are items such as leaves, dead insects, animal wastes and moist stored grains or grain products that are in the process of decaying. Homeowners may find mealworms in oatmeal, flour, or other dry goods stored in the pantry.

Habitat: Where Do Mealworms Live?

Their normal habitat is dark, cool and moist locations where there is suitable food and sheltered areas such as under rocks, logs, in animal waste accumulations and in moist, stored grain storage areas.

Reproduction & Life Cycle

Mealworms go through an egg, larval, pupal and adult stages (complete metamorphosis) and their life cycle usually is completed in about three to six months. Adult mealworm beetles only live about 30-70 days, depending on the temperature and suitability of their habitat. Read more.

Continue Learning

Mealworm Beetle Life Cycle