Why are 100's of bees swarming around my cypress pines, i cant see a hive?

These are probably honey bees. They use the sap to make propolis in the hive which is a substance they use as a cement and a sealer. They don't have many sources for it in the winter so they are getting it from your tree on warm days.They are not actually swarming. Bees swarm in the spring and only IF they have a queen, not in search of one or for the lack of one as some say.Bees leave the hive as a swarm with the old queen when a new one is born to take her place in the original hive when the hive becomes overpopulated in the spring. The bees you are seeing are just foraging and will not attact you. The are just after the sap.