You do not have to be around honey bee colonies very long before you encounter one of their most complicated group behaviors – the swarm. Beekeepers usually do not like to see a colony swarm. After all, it means that their colony split in half usually right before or during the major nectar flow of the year. Bees, on the other hand, want to swarm more than nearly anything else they do. This sets the stage for a complicated tug-of-war between colonies that want to reproduce and beekeepers who want to stop this reproduction at all costs. Herein, I discuss the marvel of the honey bee swarm. A lot of what I discuss comes from Dr. Tom Seeley’s (Professor, Cornell University) book Honeybee Democracy or from his lectures on the topic available online at https://www.youtube.com/watch?v=JnnjY823e-w and https://www.youtube.com/watch?v=dVfC0P_a43o. The book and videos are worth reviewing, especially if this is a topic that is of interest to you.
What is a swarm?
To answer the question succinctly, and to set the stage for the discussion that follows, a swarm is honey bee reproduction at the colony level. This, of course, demands additional information because one must understand what “at the colony level” means. After all, most people believe that honey bee reproduction occurs when a queen lays an egg. Of course, this is true in the simplest sense. A bee making more bees is reproduction. However, honey bees are social insects and social insects have a peculiar reproductive strategy that one can see at the colony level. Colony level reproduction is best understood within the paradigm of the superorganism concept.
Those who study social insects (ants, termites, some bees and wasps) do not look at a colony of social insects only as a collection of individuals. Instead, they look at the colony as the individual. In short, the honey bee colony can be viewed as a type of organism, a superorganism. The prefix super means above, thus suggesting a level of organization above that of the simple organism. The honey bee colony has become a unit of selection, or the most basic biological entity (cell, gene, organism, etc.) on which pressure is exerted, ultimately resulting in a change in that entity. While it is true that individual honey bees reproduce, given we know that queens lay eggs, colonies also reproduce because colonies produce more colonies. In fact, one can argue reasonably well that it is colony reproduction about which bees most care.
Think about it: if bees wanted simply to make more bees, then they would grow their colonies indefinitely, with there being no end in sight to the potential strength and size of a given colony. Yet, they do not do this. Consequently, there must be more to honey bee reproduction than just producing more bees – and there is. Honey bees want, more than anything, to make more colonies. This is important for beekeepers to know and understand. Reproduction is among the strongest drives in any organism. An organism that can reproduce goes to great lengths to make it happen. This is why bee colonies want to swarm so badly, often to the chagrin of their keepers, and why swarming is so hard for beekeepers to stop. Swarming is how honey bees survive.
Given that swarming is colony level reproduction, watching a colony swarm is watching a colony give birth. This is a very poetic way to think about swarming. I often think about a mammal giving birth when I see bees rushing out of a colony, heading to the air, with the resulting cluster of bees very much like a baby bee hive. However, Dr. Seeley notes that bee colonies reproduce much more like an apple tree than they do like a mammal. Apple trees reproduce (spread their genes) two primary ways – (1) by dropping fertilized seeds in fruit to the ground to grow new trees and (2) by spreading pollen that goes out to fertilize the seeds of other apple trees. An apple tree that has produced a seed has invested as much of itself (its DNA) in the seed as it does in the pollen that fertilizes another tree’s seed. Thus, the daughter tree growing from a seed produced by a parent tree (parent tree A) is as related to parent tree A as much as is a daughter tree growing from a seed from a second parent tree (parent tree B) that was fertilized by parent tree A’s pollen.
How, then, is honey bee colony reproduction like that of an apple tree? First, the swarm is analogous to the apple that falls away from the parent tree (the parent colony). That swarm harbors the fertilized seed (the queen) that contains the genetic material necessary to grow a new colony. The swarm, when planted in the right place, grows into a new colony of its own, one that is ready to produce its own fruit and pollen. What is the bee equivalent to pollen? Why, the drones that fly daily from the nest in search of other colonies’ seed (queens) to pollinate are. Thus, colonies drop fruit (swarms) and disperse pollen (drones) in an effort to reproduce/disperse their genes.
Stimuli leading a colony to swarm
Given that swarming is colony level reproduction and reproducing is one of the strongest drives in a honey bee colony, why do all colonies not …
