Spotlight on honey bee legs: they’re not just for dancing

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Inside: The six legs of the honey bee do much more than walk and dance. They perform dozens of chores that affect every aspect of honey bee life.

We seldom consider the legs of bees

Imagine you’re playing a word association game such as Password and your secret word is “bee.” The clues you might give to elicit that word include “honey,” “sting,” and “swarm.” But “legs”? Never. Nothing about legs reminds us of bees.

This article first appeared in American Bee Journal, Volume 163 No. 6, June 2023.

Yet bees, especially honey bees, have some of the niftiest legs in the animal kingdom. Although they don’t hold a candle to millipedes for quantity or harvestmen for length, they beat them hands-down for function. Honey bee legs are like mini Swiss army knives: creatively designed and compactly stored tools for every purpose.

The thorax is an insect’s transportation hub

Like all insects, honey bees have six legs, each arising from the thorax alongside the wings. But in honey bees, each leg pair has a unique structure, making each pair noticeably different from the others. And each pair performs unique functions for the multitasking honey bee.

Although bees use all three pairs for walking and dancing, they also perform rare feats we seldom associate with legs. For example, a honey bee’s legs including the attached feet (tarsal claws) can taste and smell! Now those are truly amazing stunts for legs and feet(s).

Features all six legs have in common

Before we look at leg differences, let’s look at their similarities. First, all bee legs have five segments. Beginning at the thorax and working out, we have the coxa, trochanter, femur, tibia, and tarsus. Some of these parts may be unfamiliar to you, but some you know, which makes them easy to learn.

For example, you have a femur in your upper leg and a tibia in your lower leg. These come together in a joint called the knee. In addition, you have a protective plate covering the joint called a kneecap or patella.

In comparison, a bee has six knees in exactly the same place — between each femur and tibia. Although most bee species have a protective shield (a kneecap of sorts) at the basal end of the rear tibia, these are conspicuously absent in honey bees. Ground-dwelling bees use these basitibial plates to brace themselves in the dirt while digging so they don’t lose traction or slip and tumble into the hole.

At the far end of your human tibia, you have a foot made of many smaller bones that aid balance and movement. Similarly, the bee foot (or tarsus) comprises five subsegments that help the bee with balance and movement.

The five subsegments of the tarsus are called tarsomeres. The first tarsomere, closest to the bee’s body, is called the basitarsus and the last one is called the pretarsus or distitarsus (the toe).1 In honey bees, the far (distal) end of the pretarsus sports two claws (called tarsal claws).

Five leg segments or six?

In older publications, it is common to find mention of six leg segments instead of five. The discrepancy involves the tarsus, and whether the pretarsus should be a separate leg segment or included in the tarsus as a fifth subsegment. Since the current literature usually names five subsegments within the tarsus, I’m using that convention. Just remember that you may see it reported differently.

Between the tarsal claws, you can find the arolium, an adhesive pad covered with tiny hairs. The pads are useful for walking on vertical or inverted surfaces and enabling the bees to navigate irregular or slippery substrates. The arolium and the tarsal claws are extensions of the pretarsus.

Pollen sticks all over a honey bee's body, even in her eyes. She needs her legs to collect and store the pollen in one convenient place, her pollen baskets.
A bee cleans pollen from all parts of her body and then sends it back to the pollen press. She even has special hairs on her forelegs to clean the pollen off her large compound eyes.

Bee legs come in different lengths

Even though all six legs of the honey bee have the same segments, each pair of legs is a different length. And it’s not surprising to learn that worker legs differ from queen legs which differ from drone legs. Because each type of bee has a unique role to play within the colony, its legs evolved to fit the job.

In worker bees, the forelegs are the shortest, followed by the mid legs, and then the hind legs. The queen’s legs follow the same pattern, but overall her legs extend farther because she has a bigger body. In addition, the queen carries her legs splayed out like a water strider, which makes them appear even longer.

Around the hive, both workers and drones keep their legs tucked under their bodies. Bees flying long distances tuck them out of the way too, although workers dangle their legs before landing, much like an airplane’s landing gear.

All insect legs follow a similar model, but they have adaptations that help them with life in their unique environment. Various types of bees have quirky takes on the same parts, many of which can help taxonomists determine a bee’s genus.

A bee leg for every purpose

With some glaring exceptions, honey bees use their legs like we use our hands and feet. Here are some everyday uses for three pairs of honey bee legs.

  • Grasping: Times are many when a bee just wants to latch on and hold tight. When the wind is tossing her flower erratically, when she and her sisters decide to build a scaffold for comb construction, or when drone dispatching appears on the agenda, those tarsal claws come in mighty handy.
  • Grooming and scratching: Bees comb their bristly articulated legs across their bodies to gather pollen and remove accumulated dirt and grime. And now and then, bees appear to take a scratch just like everyone else. Some researchers believe the European honey bee is adept at grooming away tracheal mites, something we’ve paid little attention to in recent years.2
  • Tasting and smelling: Honey bees have multiple receptors for taste and smell. We find some on the mouthparts and antennae, but surprisingly, some are on the tarsi. Hair-like sensory organs called sensilla can detect both the taste and odor of things the bee walks on. The bees send their findings to the brain, which “decides” if the substance is a suitable food source.
  • Pollen collecting: Honey bee legs play a major role in pollen acquisition, with most segments featuring hairs that facilitate collection. The density, length, and thickness of hairs vary depending on their location and exact purpose.

Some legs are better equipped than others for certain jobs, so let’s look at each pair of legs and its specialized equipment.

Features of the honey bee’s forelegs

Although the forelegs are the honey bee’s shortest pair, what they lack in length they make up in function. For example, it’s the foreleg tarsi that harbor the sensilla for taste and smell.

In addition, each foreleg has an antenna cleaner built right in. The antenna cleaner comprises two parts: a round notch in the basitarsus outfitted with stiff hairs, and a corresponding spur on the tibia.

To make it work, a bee simply lifts her foreleg over her own antenna, and then flexes her leg. This movement makes the spur close across the open notch, locking her antenna in a snug ring. Then she pulls her antenna through the ring, an action which scrapes off any pollen and debris stuck to it.

Bees clean their antennae constantly. The antennae have sensors for feeling, smelling, and tasting — all things which help the bee navigate her world. Because they are vital, antennae need immaculate cleaning and maintenance. An ingenious pair of forelegs makes this all happen.

In addition, the honey bee uses her forelegs to clean pollen from her face and compound eyes. The hairs on her eyes hold the pollen away from the eye surface, making them easier to clean.

The boring mid-legs of honey bees

I’ve heard them called boring. Although the mid-legs of the honey bee don’t have any spectacular equipment, they are certainly important. The two mid-legs aid in balance and stability. Although we humans do pretty well with two legs, and most mammals get by with four, insects need to walk in precarious places.

Bees need to walk on thrashing flowers, limpish petals, and up narrow stems. They must walk on the edges of honeycombs with deep holes all around, and they even walk on duckweed and pond scum (filamentous algae). In addition, they fight. They battle intruders and they wrestle drones out of the house when the time is right. In each of these cases, that extra pair of legs supports their movements and aids in agility.

The mid-legs also help grasp things like stamens as the bee collects pollen from flowers: The mid-legs can hang tight while the forelegs engage in collecting. In addition, the mid-legs sync with the other pairs to clean pollen from the bee’s body and pass it back toward the pollen baskets on the rear set of legs.

Mid-legs also allow “rearing up,” much like a horse. The honey bee can fight with her forelegs and mandibles while the mid-legs and rear legs work together to provide balance and support.

As useful as the mid-legs are, a honey bee can continue to function as a productive member of the colony if she loses one of her mid-legs. Conversely, losing one back leg or one foreleg results in incapacitation for the bee and she will not survive for long.

The rear four legs of washboarding bees stay in place while the front legs step forward and back. Rusty Burlew

The rear legs: especially good for storing and packing

If the mid-legs are boring, the rear legs are anything but. The rear legs are the longest and the easiest for us to recognize because of their pollen baskets. Although pollen baskets are cool in their own right, they don’t hold a candle to the equipment that fills them.

Both rear legs have a secret built-in tool for loading pollen baskets. The two-part mechanism is called a pollen press. The pollen features two flat plates hinged together on one side. One plate is on the distal end (the end farthest from the body) of the tibia, while the other plate is on the basitarsus. Recall that this joint is equivalent to a knee.

When a honey bee bends her leg, the plates pull apart, and she stuffs the open press with pollen that she collects from her body. First, she scrapes all the pollen into one place: the inside of the hind leg basitarsus. Then she combs it off the basitarsus with stiff bristles lining the edge of the pollen press called a pollen rake. She cleans the left leg with the right and the right leg with the left until the open press is full of pollen.

When you see a honey bee busily working her rear legs while standing firm with her fore- and mid-legs, this is often what she’s doing. She moves lightning-fast, cleaning and brushing and loading the press. Then all she needs to do to finish the job is extend those rear legs, one at a time.

When she straightens her leg, the plates squeeze together, closing against the pollen and forcing it up into the pollen basket. It’s like a tube of toothpaste: When you squeeze the two sides together, the paste comes out the top. Here, when the two plates are squeezed together, the pollen flows up into the pollen basket. Although it may seem backward, the pollen basket is actually filled from the bottom.

Every time the bee grooms the pollen from her body, she pushes it down to the inside of the basitarsus of the rear legs and then into the press before she gives it another squeeze. Is that cool or what?

All together now: six legs working at once

While the legs of honey bees possess unique parts that work independently for some chores, they often work together. The following activities require multiple sets of legs.

Walking: Like other insects, the nervous system of the bee coordinates the movement of the legs so they don’t get tangled up. Anyone who trips over their own two feet knows how treacherous six could become.

But according to Caron & Connor in “Honey Bee Biology,” the bees’ six legs function in sets of three, with each set forming a triangle. “The first and third leg on one side work with the middle leg of the opposite side.”3 I only noticed this once it was pointed out to me, but it virtually eliminates the trip hazard and looks kind of freaky.

Pollen packing: Another example of legs working together occurs as the bee cleans its body of pollen. A bee that has been foraging will have pollen all over, from head to foot. She needs to collect all of it and somehow get it in the pollen baskets.

In a smooth sequence, the forelegs pass the pollen to the mid-legs, which pass it to the rear legs, often crisscrossing from side to side as the left side cleans the right and vice versa. Watch a honey bee packing pollen and you will see all six legs working in harmony.

Festooning: The tarsal claws on all six feet help the honey bee grasp onto objects or onto each other. When honey bee workers form a festoon — one of those lacy-looking scaffolds — the bees hang onto each other’s legs to form intricate chains. Because the legs are strong and flexible, chain building gives bees easy access to areas that would otherwise be difficult to reach.

Pheromone distribution: All six feet deliver the footprint pheromones used for communication and colony regulation. When a worker walks across a flower petal, or across the entrance to her hive, hive mates can “read” this signal and know they are in the right place.

Washboarding: Another use for all six legs at once is washboarding. During washboarding, you will see many bees on the front of the hive, perhaps hundreds. They all face the same direction and rock back and forth in a mesmerizing display. Look carefully and you can see the rear four legs stay in one spot, while the forelegs step forward and back, forward and back.

Along with the steps, the bees do something with their mouthparts. This baffling behavior is thought to be related to cleaning, polishing, or pathogen management, yet no one knows for sure. What we do know is that it’s great fun to watch.

Honey bees in a festoon are working hard at building a comb from a starter strip. They hang together by grasping each other leg to leg. Rusty Burlew.

Please clean your feet before entry

Most beekeepers worry little about all the walking honey bees do within the hive. However, producers of comb honey obsess over it. The problem? Foragers have dirty feet. Incredibly dirty feet.

As foragers enter the hive from the great outdoors, they leave footprints everywhere. The dirt may come from outside the hive or the bees may collect dirt and bits of pollen on the trek from the hive entrance to the honey storage area. In any case, these dirty trails have a name: “travel stain.”

Travel stains can hurt a comb honey producer’s bottom line. Instead of gleaming white cappings, the potential purchaser may see a smeared darkness, reminiscent of a senescent dishrag. Or sometimes the stain resembles smeared egg yolk — like the yellow brick road, only not in a good way. These smudges result from layer upon layer of pollen laid down by thousands of feet traveling back and forth, day after day.

Some comb honey producers give their bees upper entrances to keep the foragers from stepping in brood box debris on the way to the supers. Others keep a close watch on the frames, immediately removing any that become completely capped.

When I visited a daffodil breeding center in Oregon, I had to step in a bleach bucket before entering the fields to prevent soil contamination. I’ve often thought that comb honey producers need a similar foot bath for their bees to keep them clean enough for the job.

The six-pack that keeps honey bees on their feet

The next time you’re watching your honey bees, look closely at those complex underrated legs. Try to figure out what they’re doing, how they coordinate, and where they’re stored.

Honey bee legs provide a perfect example of the enormous impact that seemingly insignificant parts of nature can have. The complexity and adaptability of honey bee legs (and feats) remind me to appreciate those small things that often go unnoticed.

References

  1. Michener CD. 2007. Bees of the World, 2nd Ed. Johns Hopkins University Press. Baltimore, MD.
  2. Danka RF and Villa JD. 1997. Evidence of auto-grooming as a mechanism of honey bee resistance to tracheal mite infestation. Journal of Apicultural Research 37(1): 39-46C.
  3. Caron DM and Connor LJ. 2013. Honey Bee Biology and Beekeeping. Wicwas Press. Kalamazoo, MI.

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