Physical Characteristics
Most people know the darkling beetle, also known as the flour beetle, for its larval form, the mealworm. The two common species of darkling beetle larvae are the dark mealworm (Tenebrio obscurus) and the yellow mealworm (T. molitor); both mealworms are around 1 1/4 inch long, smooth, hard-bodied and cylindrical, the difference being that T. obscurus larvae are yellowish-brown to blackish brown, while T. molitor larvae range from pale yellow to brownish yellow, and often are bright yellow. Adults are 1/2 to 5/8 inch long, with capsule-shaped elytra (the beetle’s hardened wing coverings) taking up the lower 2/3 of the dorsal view; the major difference is that T. obscurus is black with a dull or matte finish, where T. molitor is shiny dark brown to black.

Darkling Beetle


Mealworms are a common pantry pest, as well as a bait-hook staple for fishing and something to feed to bird, reptile or fish pets. In places where entomophagy – cooking and eating bugs – is culturally acceptable, mealworms are a popular menu item. But in the kitchen or pantry, mealworms spell trouble, because if you eat the larvae with the breakfast cereal it’s feeding upon, you may end up with a rather unpleasant tummyache. Fortunately, the darkling beetle’s preferred breeding environment is in accumulated piles of spilled grain located in dark and damp places, so if your pantry is clean and your stores of grain are kept in dry, sealed containers, you shouldn’t have a problem with mealworms.


Poor sanitation provides a harborage for mealworms and adult darkling beetles. Keep a clean kitchen and pantry, and mealworms shouldn’t be a problem. If they are, your Clark Pest Control technician will know the quickest route to controlling them.

Latin name: Tenebrio molitor, T. obscurus