Bed bugs are generally nocturnal so they aren’t easy to find during the day when there is enough light to see them. Instead, it’s easier to look for signs of a bed bug infestation instead of the actual bug itself. Molted skin or small dark stains on your bedding or upholstery are clear indicators of bed bugs. The molted skin of a bed bug looks quite similar to a popcorn kernel, although it is lighter in color. The dark stains that they leave behind are droppings that contain human blood.