Dark/Yellow Mealworms

Tenebrio spp.

Dark Mealworm

Top: Dark mealworm (Clemson University, Bugwood.org)  Bottom: Dark mealworm adult (Pest and Diseases Image Library, Bugwood.org)

yellow mealworm

Top: Yellow mealworm adult; Bottom: Yellow mealworm (Clemson University, Bugwood.org)


Dark mealworm

  • adult: dull black or very dark brown
  • larvae: up to 1 1/4 inches long, smooth, cylindrical and brownish to dark yellow

Yellow mealworm

  • adult: shiny black to dark brown
  • larvae: up to 1 1/4 inches long; smooth, cylindrical and golden-yellow 

Nesting Habits

  • lay eggs singly or in clusters in food sources
  • prefer dark, damp and undisturbed environments
  • larvae can migrate from infested areas


  • old or moldy grain, oats or seeds


  • presence indicates a lack of proper sanitation
  • eggs and/or larvae ingested with breakfast foods can cause gastrointestinal discomfort

IPM Recommendations

  • Improve sanitation procedures in affected areas.
  • Inspect all incoming food items for pests.
  • Store food items in pest-proof containers. 
  • Dispose of infested food items.
  • Keep moisture low in food storage areas by improving ventilation.
  • Keep food in regular rotation.

Additional Resources

IPM for Fabric and Pantry Pests: Integrated Pest Management in Sensitive Environments (University of Nebraska-Lincoln Extension)