Adults have been found feeding on carcasses in poultry houses. The virus causing Marek's disease of poultry and poultry tapeworms may be transmitted by darkling beetles. Occasionally young birds or sick birds may be attacked by darkling beetles. Eggs hatch in 4-7 days. Tiny lesser mealworms hatch and develop in the litter.
Lesser mealworms develop through several stages before they molt into the pupal stage.
Larval development takes up to 7 weeks. Mature larvae seek a sheltered place to pupate because the darkling beetles prey on the lesser mealworms. Most of the damage to insulation is done by lesser mealworms seeking a safe place to pupate. The pupal stage lasts 7-11 days. Newly molted adult beetles are tannish-brown and darken slowly to black.