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American Bee Journal

The Spectrum of Bee Sociality

By December 20, 2021No Comments

When we think of bees, we usually think of social creatures. We often see drawings of bees circling a bulbous nest dangling from a tree. The bees look down at us and scowl or smile, depending on the artist’s worldview.

In truth, bees have an enormous range of social behaviors. The eusocial (meaning truly social) species like honey bees cap one end of the spectrum, while solitary bees such as orchard mason bees mark the other. But between the two extremes lies a fascinating amalgam of alternative lifestyles, each with pros and cons.

Honey bee aficionados sometimes try to convince us that eusociality is the ultimate goal, the pinnacle that other bees covet. But the record of natural history does not support that view. In fact, the fossil record shows that some species moved toward sociality before reversing course, evolving back toward a solitary lifestyle.1 When you realize that both solitary and eusocial species have endured for eons, it’s hard to say that one is better than the other. Both seem to work just fine.

 

Eusocial insects are everywhere

All seven species of Apis are eusocial, but they are certainly not the only bees — or the only insects — that live that way. Bumble bees, all of them, are eusocial, as are the stingless bees. In addition, we have eusocial wasps of various types, including those that live in the globose paper abodes.

I’m the unwitting owner of a ginormous paper abode at this very moment. It hangs in the upper branches of a cedar tree and spews bald-faced hornets, Dolichovespula maculata, which feed on my equally eusocial honey bees. I spent all summer looking for the nest, only to discover it right above my head as I walk out the front door.

Beneath my house lives a colony of highly eusocial ants. They bloom every August and crawl up the siding of my house in waves that make me itch. After I spray them to ground with a garden hose, they disappear for another year.

In spring, teeming hordes of red-and-black fire ants appear at the top of the hill behind my house. They ever-so-socially writhe over one another as they shape piles of fir needles into two-foot pyramids that pulsate with formic acid.

Luckily, I don’t have termites. Those pests, pleasantly known as social cockroaches, are not even in the order Hymenoptera, but they managed to evolve a social structure similar to that of bees, ants, and wasps. So you see? Eusocial insects are ubiquitous.

 

Pros and cons of the eusocial life

Some advantages of the eusocial life are obvious, such as defense. The idea of getting stung by many bees is more off-putting than being stung by one, a thought that keeps intruders wary. The same holds for fire ants. If you’ve ever stepped on a fire-ant hill and had them run up your legs, you know the feeling of terror.

Not only are the numbers intimidating, but a large group of individuals can keep many eyes on a developing situation. See that skunk coming toward us? Prepare to pounce!

Cooperative food and water acquisition is another benefit. When many individuals are hunting for supplies, finding the things they need is more likely. A group can certainly cover more ground than a single bee, and the group can collect it more efficiently. On the other hand, the colony needs more supplies as the group gets bigger, and there is more to lose should it fail.

Highly eusocial insects are more likely to overwinter, so cooperative warming of the brood nest becomes important. Solitary bees do not keep each other warm, but neither do they have the need. Most solitary bees hibernate as either pupae or adults until the weather warms in spring.

Density itself engenders problems. Large colonies are easily visible and make excellent targets for hungry animals like bears. Competition for food within a colony can be intense, too, and if food becomes short in the winter, the entire colony can perish. And as beekeepers know, disease and parasite transmission among colony members is treacherously efficient.

 

The spectrum of sociality

If you look at sociality as a continuum, you will find a wide range of variations that fall between the extremes of solitary and eusocial. I’m fond of saying that honey bees are outliers in the bee world, and this is especially true of sociality. Honey bees are at the very pinnacle of cooperative living, but that doesn’t mean other bees are inferior, only different.

 

Solitary bees

At the “simple” end of the spectrum, you will find the solitary bees. However, when you examine the day-to-day existence of these bees, you will find their lives anything but simple.

A solitary female is truly the full-meal deal. Except for a brief tryst with an impatient male, she performs every step of the child-rearing process by herself with no help from parents, siblings, neighbors, in-laws, or men. She is the home builder, egg layer, provisioner, security guard, and maintenance staff. A solitary bee mom works her entire life without ever seeing results. She’s born alone, works alone, dies alone, and never even meets the kids. Now that’s rough.

Who are these intrepid bees who work so hard and ask so little? Most of them. Most bee species are solitary, and everything else is an exception. The following list details some of the major types of sociality, but note that all bees do not agree on the details and neither do all melittologists. The definitions of social types are as fluid as the bees within. In the descriptions below, I’ve adapted the groups proposed by O’Toole & Raw in their 2004 book, “Bees of the World.”2

 

Communal bees

The first step up from a purely solitary existence is communal living. I think of these bees as the condo dwellers. The members of the condo association have a common entrance — the front door — and a vestibule of sorts that leads to individual units. Once inside, each female maintains her own unit, separate from everyone else. She excavates and maintains her own brood cells, and collects provisions for her offspring. Except for that common entrance, she is like any other solitary bee, building, and provisioning until she dies, without ever meeting her spawn.

Forty or fifty females may share the common area, barely nodding to one another as they come and go. But so much activity at the front door is a safety feature. The entrance is rarely unguarded as bees come and go, and someone is usually on hand to wrestle an intruder. They have a built-in neighborhood watch.3

Communal living is not mandatory for most of the bees in this group. In species where communal living is common, some individuals will inevitably choose the solitary life. So just across the street from the condo, you may find single-family homes.

Researchers believe communal arrangements begin when several sisters emerge inside a single-family nest and decide to expand the nest rather than go out and find new ones. This is thought to be the safer option for both the individuals and the species.

 

Quasisocial bees

Yet another arrangement is called quasisocial. Quasisocial living occurs when several bees in a nest emerge at the same time. There is no “mother” in attendance because she is long gone, having laid her eggs, provisioned them with food, and left. For a time, these young females — who are sisters or half-sisters — continue to share the natal nest, much like the communal bees.

However, instead of each bee minding her own business, one female will dominate and take over the nest. She will redecorate, repairing any damaged brood cells, and building new ones. Then she will lay eggs.

For a while, the sister bees will help with the renovations, foraging, and provisioning. The period of cooperative homemaking is the quasisocial period. It is usually quite short and, after a few days, the once-helpful sisters go out and find nests of their own.

Because this type of social arrangement is temporary, it’s difficult to define and hard to detect. Like a communal nest, it is dynamic, changing with the ….

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