Casting light on honey bee castes
Honey bees come in two sexes and two castes—not three castes. In fact, the definition of “caste” is about the only thing I remember from my college entomology courses, and that’s because the professors drilled it into our little brains incessantly.
Even more prevalent than the “honey bees never sleep” myth is the “honey bees have three castes” myth. In fact, it’s hard to find a reference that doesn’t erroneously mention the three castes of honey bees.
However, if you understand the definition of caste, you will see it doesn’t work that way. Simply put, bees are divided into two sexes, male and female, and the females are further divided into two castes, queens and workers. As a result you have three types of bees: males and two castes of females.
Some useful definitions
Here is a good definition from The ABC & XYZ of Bee Culture:
A caste refers to a group of individuals of the same sex that behave similarly to each other but differently from other members of their sex.
Honey bee workers behave like other honey bee workers, but all workers behave differently than the queen. Since both types are of the same sex, it means workers and queens are two different castes of female.
The definition continues:
Behavioral differences among castes are usually accompanied by specific differences in morphology and /or physiology.
Indeed, the behavioral difference between workers and queens are accompanied by differences in form and function.
In the honey bee world, at least, all men are created equal—so the males (drones) have no castes. If you add zero castes to two castes you get a total of two castes, not three.
Here is the glossary definition from The Beekeeper’s Handbook by Diana Sammataro and Alphonse Avitabile:
Caste: The two types of female bees: workers and queens. Drones are male bees and are therefore not a caste.
And here’s another clear definition from Betterbee.com:
Castes – a term used to describe social insects of the same species and sex that differ in morphology or behavior. In honey bees there are two castes, workers and queens. The drones are a different sex and therefore not included.
A chapter in The Hive and the Honey Bee (2015) called “Honey Bee Sociogenomics” explains that castes are determined by environmental signals. In the case of the honey bee, the signal is the type of food supplied to a developing larva. But no amount of royal jelly will turn a drone into a queen because the genetics are totally different: drones only have one set of chromosomes, not two. Indirectly, this explains why a drone is not a caste.
“In other words, caste determination is influenced by an environmental signal, nutrition, which triggers molecular changes that result in the development of either a worker or queen bee.
Castes in other species
Other social insects have castes as well. Ants, I’m told, can have more than two castes of female and some termites have castes of males.
We can make this much more complicated by considering temporal castes—a topic I will tackle at another time. Meanwhile, just remember that honey bees come in three types, but only two castes.