Sometimes bees take up residency in the basement wall or ceiling. Bees may end up inside the basement when attracted to a light that was left on or the natural basement light from a window. Bees that end up in the basement include honeybees, wasps, hornets, and yellow jackets. As mentioned, often the hive or nest is within the basement ceiling or wall.
Inspecting the outside area between 10 am and 5 pm can help find out were the bees are located. With honeybees, yellowjackets, and hornets there should be a good amount of activity somewhere outside near the Basement. With wasps, and bumblebees there will be lesser activity requiring more patience. You can use this Bee id chart to help identify the type of bee your seeing.
If they are honeybees, removing the hive and honeycomb is usually important to solving the problem, otherwise you may end up with recurring bee problems in addition to attracting other critters to your basement area. Learn more here about how to get rid of bees in the wall including some dos and donts for solving a bee problem.
In the case of honeybees most people recommend calling a beekeeper to remove the bees.