Yellow Mealworm

Tenebrio molitor, belonging to the family Tenebrionidae, exhibits complete metamorphosis. Larvae are distinctively cylindrical, smooth, and hard-bodied, ranging from pale yellow to golden-brown, with prominent segmentation and reaching 25–30 mm prior to pupation. The pupal stage, typically lasting 7–23 days, is exarate and white to yellowish-brown. Adults are ovate, dull black or dark brown beetles, 12–18 mm in length, with finely punctate elytra and distinct antennal clubs. Under optimal conditions (25–30°C and 70% RH), the full life cycle can be completed in 3–4 months, though it often extends to 6–12 months. Females lay up to 500 eggs individually or in small clusters over a period of several months, often embedded in foodstuff.

Yellow mealworm larvae are primarily nocturnal but will forage during the day in undisturbed, dark environments. They are detritivores, feeding on decaying organic matter, milled grain products, and animal feed. While adults possess wings, they are generally reluctant fliers, preferring to crawl, especially when disturbed. Larvae tunnel extensively through their food source, creating galleries and leaving behind characteristic frass and shed exoskeletons, which can accumulate significantly in infested materials, potentially causing allergenicity. This continuous feeding and movement degrade the quality and marketability of infested products. Communication is largely absent from the social structure beyond localized aggregation based on food availability.