The board of trustees of the firemen’s insurance and inspection fund in cities and towns, if composed of three, consists of the mayor, the councilman in charge of the fire department or the chairman of the fire committee, and the chief of the fire department. The board in cities and towns, if composed of five, consists of the chairman of the board of fire masters or the chairman of the fire committee, the chief of the fire department, the city or town treasurer, and two citizens, one to be appointed by the mayor and one to be appointed by the chief of the fire department, both to be confirmed by the governing body of the city or town. The term of office of the last two named members of the board is four years and until their successors are appointed and confirmed and qualify for office.