Waste management: even the bees do it

I shivered in the evening wind as a full moon ripped through the horizon like the morning sun. It looked white hot, but no warmth followed it into the sky. Huddled in my sleeping bag, I made a mental inventory of the desert sounds.

As a youngster, I always thought the desert would be quiet at night, but it’s anything but. The first odd thing I noticed was the song of frogs. They sounded like tree frogs, those green dime-sized amphibians that frolic through the flowers and stick to walls and window casements. But this was the Oregon high desert, not Frogtown. Was I misinterpreting the sound?

From somewhere downslope came the complaint of cattle, and beyond that a chorus of coyotes. First one coyote called and then another until they all burbled at once, their combined voices sounding like water gurgling in a hot cauldron. They all talked together until something caught their attention, commanding instant silence. No wonder the cattle were restless.

Sanitizing the forest floor

I awoke early enough to see a few stars winking from a cloudless sky. The moon was gone, replaced by a faint lightness. The nocturnal mammals were now silent, replaced by calling birds, prattling chipmunks, and a distant chainsaw groaning into an early start.

Although the air was too cold for bees, I hunted for flowers, trying to find places I might later search for pollinators. Frogs, too. As I scoured the stark, rocky ground for tiny blooms, I noticed a chunk of deer scat — one solitary piece — traveling across the forest floor.

Now, dung on the run is worth a closer look, so I got down on hands and knees. There, amongst several handsome piles of droppings, I found a glistening black beetle hard at work. I was overjoyed to find a companion.

She — I assume it was she — tugged at a large pellet of dry poop. With her prize clenched in her mandibles, she backed toward a small hole in the ground bookmarked by two flat rocks. She tugged and twisted, edging the thing closer to home by fits and starts. The turd was as long as the beetle but wider and taller, roughly the size of an old-fashioned jelly bean.

I watched for multiple minutes until she backed into her hole, still clamped into the dirigible-shaped treasure. After she disappeared, the dung continued to dance and shimmy at the entrance as she pulled and tugged. “You need to rethink this,” I said to her. No way was that fat prize going to fit into a tube no bigger than a soda straw.

I was amused and fascinated by her determination until, with a pop I could only imagine, the entire thing disappeared into the hole. I couldn’t believe my eyes. It was gone, she was gone, and the entrance was no bigger than before. Like stuffing an oversized cork in a wine bottle, it required a certain finesse.

Sitting cross-legged in the dirt, I waited, hoping to see a repeat performance of this marvelous trick. But she never reappeared. I was tempted to dig into the ground to see where she put the thing, but since she made such a neat job of it, I didn’t have the heart to meddle.

More than just pollinators

Whenever people talk about the insect apocalypse, I think not of pollinators but of all the insects that renew and cleanse our environment, the ones that eat dung, and the ones that feast on dead and decaying plants, animals, fungi, and microbes.

Where would we be without them if not in a cesspool of unmentionables? It’s far too easy to demonize the bugs that bother us, forgetting about the ones that keep our planet habitable. It’s unconscionable that the chemicals we choose to destroy the insects we dislike also kill the ones we depend on. Dung eaters are no less important than pollinators.

Why farther is better

Waste management is a universal problem, and honey bees have their own fecal woes. But as you might expect, all bees have unique methods of dealing with defecation that evolved throughout the bee families.

When we think of honey bee poop, we usually picture yellow rain, the kind that falls from the sky leaving sticky blobs that adhere to cars and picnic tables. Many people — men in particular — believe that honey bees actually enjoy this activity, practicing airstrikes on especially shiny or recently cleaned objects.

More likely, our beehives are close to our houses and cars, which means the density of droplets is high. According to the inverse square law, the distribution of a quantity of something such as sound, illumination, or bee poop is inversely proportional to the square of the distance from its source. Because bees radiate from a point source (the hive) into three-dimensional space, the density of the droplets decreases as you move farther away.

Okay, I know my interpretation is a stretch because bees don’t radiate evenly. In fact, they go wherever they please. But you get the idea. When avoiding bee poop, farther is better.

An unlikely ecosystem service

Ultimately, this sticky substance — at least the portion not stuck to your treasured possessions — gets washed into the soil where it decomposes, providing nutrients for plants and soil-borne organisms. All bees provide this ecosystem service, although it’s hard to think of it as a service while you’re scrubbing it from your vinyl siding. Still, it’s a straightforward process, wildly efficient, and easy to understand. And just think, the bees provide aerial application without the use of fossil fuels!

Ecosystem services are all the processes that allow humans to survive on planet Earth. These services, inherent in the natural world, are categorized and analyzed in various ways, but we couldn’t exist without them. For example, photosynthesis turns sunlight, water, and carbon dioxide into oxygen and food energy, and bee poop fertilizes trees, tomatoes, and toadstools.

Other services include food production, water purification, erosion control, flood control, climate regulation, and, of course, pollination and decomposition. The list is nearly endless.

Children are trouble

Just like human children, the immature stages of bees have a much more complex system of waste management than the adults, one that requires planning. After all, larval bees eat like crazy, swallowing pollen, nectar, and assorted secretions without ever leaving the natal cell. Managing the outfall from all that eating is a fascinating aspect of bee science and more complex than simply buying a truckload of diapers.

Depending on the species, defecation doesn’t begin until the late larval stages, usually during the fifth larval instar, although some begin as early as the third instar.¹ The delay is assured because the two ends of a bee’s digestive system — the receiving part and the sending part — are not connected until the very last moment. In honey bees, this connection is made during the capped larval stage, known as the prepupal stage, just before cocoon spinning.

Because the cells are capped, the nurses cannot serve more food to the baby bees. But the capping also prevents the larval feces from being removed. The answer to this conundrum is simple — just weave the feces into the fabric of the cocoon.

Environmental history from the scrap heap

To spin a cocoon, a honey bee larva secretes a continuous silken fiber from the spinneret between the two maxillae. The larva gyrates, tumbles, and somersaults as she squeezes the thread from her body, wrapping the fiber into a silken shroud. While the larva is weaving, it is also collecting bits and pieces of the waste, storing it discreetly between the threads of the cocoon, just like seed beads in a shawl. Careful timing of cocoon building and excretion keeps the feces from contaminating the body of the developing bee.

Bumble bee larvae also weave their excrement into cocoons. According to Kearns and Thomson, “accumulated larval feces are voided, then smeared on the wall of the cocoon, where they help form the structure.” Because the feces contain the indigestible and identifiable outer shells of pollen grains, palynologists can determine what the larval bumble bees ate. In addition, museum specimens can show us what bumble bee larvae ate in the past, and compare their diets to the modern bee diet.²

Alt management techniques

Not all bee species spin cocoons, and of those that do, not all weave their excrement into it. After some solitary larval bees finish eating their supersize fast-food feast, they defecate at one end of their cell before cocoon-building, allowing them to skip the fecal embellishments. Lucky bees in this group include the orchard mason bees commonly used for fruit tree pollination.

Bee larvae that do not spin a protective cocoon have developed other ways to separate themselves and their food supply from the unseemly mess. Some species pile the extruded waste in a particular spot, perhaps choosing the front of the cell while others prefer the back or the sides. When the material is soft, some larvae trowel it onto the walls like plaster, and some circle the perimeter of the cells with a line of excrement at the widest part, sort of like a picture rail.

Some bees just pile the excrement on their stomachs in a lump that looks a bit like a beer belly, then curl themselves protectively around it. Other larvae have projections that stick out from their bodies like the legs of a short stool.³ These projections, called dorsal tubercules, hold the larval bodies away from the accumulating unpleasantness. To picture it, just imagine a caterpillar on two rows of stilts.

Even varroa mites follow rigid rules for waste management. The mites leave mounds of excrement, composed mostly of guanine, on the inside walls of the brood cells, looking like bright white globs.

Feces and fungus

Some melittologists believe that fecal material stored within the brood cells may facilitate the growth of some fungal infections, including chalkbrood.⁴ In certain species such as honey bees, alkali bees, and alfalfa leafcutting bees, chalkbrood can be a severe and recurrent problem.

However, because feces isn’t the only source of spores, we don’t know how often fungal disease can be blamed on waste management. Instead, the nectar and pollen that are fed to larvae may be the more important source of disease. Since infections seem to resurface frequently where other diseased bees roam, it appears that flowers are a likely point of transfer.

Pollinator problem-solving

As I watch the creatures of the earth solve their day-to-day problems, it gives me hope for humankind. We need to remember that most problems have solutions. We simply need to give our creative energies free rein so we can think outside of “accepted” management protocols.

With so many crises occurring around the world, perhaps we should take a lesson from the smallest creatures as they tackle their mundane problems. Creative thinking and a healthy dollop of humility could take us a long, long way.

Rusty
Honey Bee Suite

References

1. O’Toole C and Raw A. 2004. Bees of the World, Facts on File edition (pp 18-19). Cassel Illustrated, London.
2. Kearns CA and Thomson JD. 2001. The Natural History of Bumblebees (p.24). University Press of Colorado. Boulder.
3. Danforth BN, Minckley RL, and Neff JL. 2019. The Solitary Bees: Biology, Evolution, and Conservation (p 45). Princeton University Press, Princeton NJ.
4. Danforth BN, Minckley RL, and Neff JL. 2019. (p 227).