Bee societies – from sleeping males to superorganisms
As we saw last week, bee societies are very variate. Though there are several definitions, there is no black and white, no linearity. This week, I want to give you some examples for associations between individuals, that may further clarify the concepts. But first, let’s hear what Charles D. Michener said in his book “The Social Behavior of Bees”:
The kinds and amount of division of labor and communication among bees in colonies vary greatly. Man being a classifying animal, a classification of the social relationships has been developed.
Keep that in mind. These classifications are a result of the human need to put things in order. They help us to understand, give us a framework. Nothing else. I stress that because you will see that the classifications often don’t really work.
Are these already societies?
Let’s begin with the males. Male bees are usually neglected, studying bees is mostly about looking at the females. But, trying to understand bee societies, males do something interesting. They form sleeping clusters. These are no societies or colonies in the most narrow sense, but, there is interaction between the individuals. They come together at a distinct place, sometimes every night, and sleep in groups. I’ve never seen it, so I was very jealous when my colleague and friend Antonio Nanetti sent me the photo above asking “Who are these guys and what are they doing?!”. Since then, I look into every poppy I happen to see in the early morning or evening. I was never lucky. But back to the sleeping clusters: In that poppy, several male Longhorn Bees were coming together for the night. Often, sleeping clusters are outside flowers, the males cling to a stem with their mandibles or legs. That looks really cute, at least I think so.
Coming back to the females: the corresponding level of sleeping clusters may be the nesting aggregations we already discussed last week. For some species these are quite characteristic, sometimes different species nest together at one spot. I’ve seen this during a study in apple orchards in England: on “Orchard 6” there was a spot where two mining bee species (the Ashy Mining Bee, Andrena cineraria and the Grey-patched Mining Bee, A. nitida) nested together in an area of perhaps 2m². There were several dozens of nests and I’ve observed them in two years at exactly the same spot. But nesting in aggregations isn’t mandatory in these species. You also find single, scattered nests.
Primitive or not?
Now things begin to be complicated. There is a bee family that regularly drives me mad, mainly because I can almost never ID them in the field. But they aren’t easy also concerning the social part. I’m speaking about halictid bees. Some species are solitary. Some are communal, i.e. a group of females using the same nest, but everyone provides only her own cells. There are also semisocial species, which means that a group of females lives together, there is division of labour and there are some females that reproduce and others that “help”, though still fertile. When I see halictid nests, I never know what social structure they may have. Which I cannot look up, because I don’t know what species they are.
As I said, they drive me crazy. In Italy, I once also saw two females, with different coloured pollen, digging at the same nest entrance. Were they communal? Helper females of a semisocial species? And where are these photos??? At least for the latter I hope to find an answer some day.
Usually, the bee societies we discussed to this point involve individuals from a single generation. “Truly social” (i.e. eusocial) bees however should consist of colonies in which individuals of two generations collaborate, mothers and daughters. Like in bumblebees and honey bees. But in bumblebees there is a “subsocial” phase, in which the queen cares all alone for her offspring. Bumblebees are referred to as “primitively eusocial” and here the definitions begin to be very vague. I don’t like the word “primitive” anyway, because it gives a value to something. When comparing “primitively eusocial” and “highly eusocial” species, you would think the highly eusocial is better. But why should this be true? The different ways of social organisation are just that. Different.
Complex bee societies
But let’s stay with the classification, at the end it makes it easier. Highly eusocial bee species have specialized to an extreme extent on division of labour and cooperation. So much, that the queen couldn’t survive alone anymore. She needs the help from the workers for feeding, for providing the cells in which she lays the eggs. Colonies of highly eusocial bee species are very large: colonies of the Western Honey Bee, for instance, at its peak of development consists in average of 35,000 worker bees. I know, higher numbers circulate out there. But in 20 years with thousands of colonies I had under my hands I never saw honey bee colonies with 80,000 workers. Nor did more experienced colleagues than me. But anyway, the important thing in this context is not only the size of the colony, but also that they persist for several years as a colony.
Honey bee colonies are often referred to as a “superorganism”, meaning that though thousands of individual animals live in a colony, they behave as a unit, as an organism. This concept is another classification with some problems, but it’s also helpful sometimes. First, it helps to explain why we need to look at the colony level when talking about honey bee health. Then, it explains why they can buffer so many adverse conditions and still stay a functional unit. Finally, it helps to consider that a colony is more than just the some of adults, brood cells and stores. Which, in my work, is often important to evaluate data from studies.
But to come back to the most “simple” way of bee societies, the aggregations. Also highly eusocial bee species form aggregations. The Giant Honey Bee often nests in “bee trees“. This species builds a single giant comb hanging on branches – not in cavities like the Western Honey Bee. And as if this wouldn’t be impressive enough, they “aggregate” in some trees. So is a nesting aggregation really the most simple form of a bee society?