These are called minute fungus beetles. In the construction industry, they are often called new house beetles. As their name implies, the larvae and adults feed on molds and mildews. In modern construction, many homes are so tightly sealed up to ensure that cool or warm air is not being lost that any moisture that was in the construction lumber or other materials has a difficult "gassing out." This moisture can condense on the outside wall or on the plasterboard surfaces and allow for a thin layer of mold to form. These molds are rarely of concern to humans, but can serve as food for the fungus beetle larvae. This can continue for a year or two after construction of a new home, but when the heating and air-conditioning systems begin to dry the ambient air, this will remove any remaining moisture out of the walls and the molds will disappear, as will the beetles. You are on the right path of getting dehumidifiers to hasten the drying down of the construction materials.  The adult beetles are often attracted to sunlight, so they will often accumulate in window sills.  Cooking, especially if you cook a lot of pasta or soups, can cause some moisture problems in that area, so check your kitchen ventilation system to ensure that it is removing excessive cooking moisture. Same for bathrooms. Be sure to run the air vent when using the shower or bath to help remove excessive steam.

If these beetles persist for more than two seasons, this is an indication that there is a vapor barrier and/or air exchange issue that is not removing the moisture that can accumulate in a tightly sealed home from regular human activities. This may need to be checked out by the company that constructed your home.