Visual Reference Library - Insects

Yellow Mealworm (Tenebrio molitor)
Dark Mealworm (Tenebrio obscurus)
Length: Approx. 12 mm 
The adult is a dark brown or black beetle about 12mm long. Both yellow mealworms and dark mealworms have well-developed wings and are attracted to light. Yellow mealworm adults are shiny, dark-brown or black, whereas dark mealworm adults are dull, pitchy black.and warehouse beetles.
Mealworms have a smooth, highly polished, shiny, elongate, hard, cylindrical (wormlike) body about 3mm thick and up to 32mm long at maturity. Young larvae are white, darkening with age. Larvae of yellow mealworms are honey-yellow, while dark mealworms are dark-brown.
The larva can do serious injury to whole grains in storage for long periods. The majority of the damage is largely limited to contamination of the products by the worms and their waste products.

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Last updated December 2016