Complex sentence: Queens are rare among a brood since only one mated queen is needed for each hive.An estimated 0.2% of a brood is made up of queens and this rate does not vary with the seasons.
Split into simpler sentences: Queens are rare among a brood since there is only one mated queen for each hive. Proto estimates that about 0.2% of a brood is made up of queens and this rate does not vary with the seasons.