It happens every spring in temperate regions of the world. Just as surely as the days get longer, the grass turns green and the flowers bloom, the social insects swarm.
In general, the term swarm is used to describe any aggregation of animals. It could be a group of birds or even snakes. For most of us, the term is used to describe a group of insects, such as mosquitoes or locusts.
Social insects use swarming as a process to establish new colonies. Four groups of insects have species that communally live in colonies. These include all termites and ants. Also some wasps, and two species of social bees - bumble bees and honey bees.
Scientists call these colony-living insects social. All such species have at least three characteristics in common. They have a queen. All have a division of labor where groups of individuals do different jobs. And all provide care for their young.
There are two types of social insects. Some, including all species of ants and termites and the honey bees have permanent colonies, which last for more than one year. Other social insects have colonies that exist only during the growing season; these are called annual colonies. All social wasps have annual colonies. So do all species of bumble bees.
So what is going on when social insects swarm? In all social insects, except for the honey bees, swarming is associated only with production of winged forms of both male and female individuals. The winged forms, called reproductives, leave the nest of an ant or termite colony on a mating flight. Once the female is mated, she will seek a suitable location for a nest site. In the nest site, she will lay a few eggs and care for the young that hatch. Once the young mature, they will take over the duties of raising the next workers. That is how new colonies of ants or termites get established.
In honey bees, the swarming process is somewhat different and a bit more complex than in other social insects. The honey bee colony doesn't just produce male and female insects to send out into the world; it also generates a group of colonizers to send on a mission. That group includes the old queen and some workers from her established colony. Such a group of honey bees is known as a swarm, and their mission is to start a new colony.
The honey bee swarming process begins with the production of males, called drones, and reproductive females called queens. Drones come from unfertilized eggs, and that is why it is said that a male honey bee has a mother but no father. Female honey bees result from fertilized eggs; they will be either workers or queens, depending on the quality of food that they receive. The queens are larger than the workers and must be raised in special chambers, known appropriately as queen cells.
In a honey bee colony, several things have to happen before the colony produces a swarm. First, a number of drones are produced, sometimes as many as 3,000 in a hive. These drones leave the colony at various times during the day and go out and fly around in areas known as drone zones.
The colony will also produce several queen cells. The first queen to emerge does not like competition so she proceeds to find other queen cells and will sting the developing queens to death. The new queen will then go on a mating flight where she will fly into a drone zone and mate with as many as six drones. The mated queen will return to her hive.
Back in the hive, the bees know that a new reproductive queen has returned and the hive prepares to swarm. The worker bees literally pack a lunch for the trip - they fill their crops with honey. The old queen and about 10,000 workers, primarily younger bees, will leave the hive.
These airborne bees swarm around the queen as she flies from the hive. When the queen lands, the other bees cluster around her forming a ball of bees. The bees will stay in that location until a suitable nest site is discovered. Then, the swarm will take to the wing again, this time on the way to their new home. For honey bees, it takes a swarm to start a new colony.