Diatomaceous Earth may be useful for killing bugs in walls. Light sockets and phone jacks provide a highway for bugs to travel from one infested room to another or one infested apartment or another. They also function as a hide-out for them during daytime hours, when they might be more visible. By cutting off this avenue, it will prevent them from traveling and create an airtight barrier, which may reduce your energy bills. Diatomaceous Earth kills insects through desiccation. They will generally die within 24 hours of contact with diatomaceous earth. Simply, open the jack, by removing the screws. Squeeze in diatomaceous earth. Seal the jack with silicon glue, when you replace it.
Have an iPhone? Check out all 200+ new features coming in iOS 13.