In the 1900’s Dr. Charles Campbell, from San Antonio, Texas, advocated that bats could control mosquito populations, and therefore malaria, with less expense and human effort than other methods.
He came up with a pioneering design for a Bat Roost equipped with “all the conveniences any little bat heart could possibly desire”.
The first one was built in spring 1911 next to Mitchell’s Lake, ten miles south of San Antonio. Malaria cases in the neighborhood decreased sharply and the Campbell tower was followed by more than a dozen more built to the same design, one as far afield as Italy. They were used until the 1950’s.
From Venue and here