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Why don’t bees have lungs?

For my brilliant friend, Iris, who rightly calls my scientific perspective two parts beautiful and inspiring and one part absolutely horrifying, and who really, really likes reminding me that bees don’t have lungs.

On April 15th, 2019, the world watched in horror as a thousand years of sacred innovation and artistry collapsed in ash and rubble. Thankfully, no humans were harmed in the fire, but people were concerned about the honeybee colonies that lived high atop the rooftops of Notre Dame de Paris. How could they possibly survive the smoke and ash pouring from the crumbling spires?

When the skies finally cleared, the city breathed a sigh of relief at the familiar sight of bees buzzing around the eaves of the cathedral. The bees were unharmed. It seemed like a miracle from Ambrose, patron saint of bees and their keepers.

A lovely thought, but what actually saved les abeilles was not divine intervention, but evolution. Since bees don’t have lungs, they don’t suffocate from heightened levels of carbon dioxide in their bodies. It just makes them a little tipsy. Beekeepers have used this little smoking trick for centuries to sedate the colonies so they can safely harvest the bees’ honey.

Hang on a second, bees don’t have lungs?

Of course not. Bees are insects, and insects don’t have lungs. For that matter, neither do 98.5%* of all animals alive today. That includes all invertebrates, most fish, and one group of salamanders that breathe directly through their skin. I thought this was common knowledge. Yet nearly everyone I told blinked at me in disbelief: but how can they breathe without lungs?

Quite well, actually! Bees breathe through an intricate system of hollow tubes called tracheae which are essentially extensions of their hard exoskeleton, the outer-body shell that keeps their structure rigid much like our endo-skeletons maintain our shape. Instead of filtering oxygen through the bloodstream, which in bees is called haemolymph and which functions only in nutrient transport, tracheae facilitate the flow of oxygen directly to the muscles. Air first enters through pores in their sides called spiracles, which open and close as bees contract the muscles of their abdomens. Bees aren’t grooving to the Bee Gees when they bob their little bums up and down, but they are stayin’ alive. Once inside the tracheae, air simply diffuses from high concentrations at the surface to lower concentrations where the tubes connect directly to muscle and organ tissue, forcing out the fluid that fills their insides at rest.

There is a catch, however. Because air flows by passive diffusion through the body cavity, the system only works if the body is small enough for air to reach the end of the tube and return. This is why giant insects today are a biological impossibility- the bigger they are, the more easily they can suffocate from lack of oxygen or drown in their own body fluids. Sorry, Mothra. Godzilla and his 500 pound lungs win this battle. 400-200 million years ago, when atmospheric oxygen content was about 15% higher than it is today, the story was very different. Back then, giant insects like meter-long dragonflies breathed easy in the Carboniferous fern forests. Bees didn’t come around until a hundred million years after oxygen fell to near modern day levels. Sadly, they never got to be yellow-jacked.

Body size could also contribute to why we tetrapods (four-limbed land vertebrates plus 2 wonky fish) can’t have the ultra-efficient respiration of our distant hexapod relatives. We’re simply too big for such a system to work. We need the powerful muscles driving our respiratory and circulatory systems to pump oxygen to our extremities. Of course, there are thousands of other contributing factors, most notably the 500 million years of evolutionary distance between the vertebrate and insect lineages.

It isn’t your fault for bumbling through life without this information. Our perspectives are constrained by our humanness, just as bees’ perspectives are limited by their bee-ness. Since our own bodies function relatively well, we assume that every other creature’s anatomy must work like ours. Perhaps bees believe that we have spiracles located under our armpits. As biologists, we challenge ourselves to transcend our human biases so we can think creatively and imaginatively about other lives.

Bees are so far removed from our experience. They breathe without lungs, crawl with three pairs of limbs and a hairy external skeleton, fly with four waxy wings, follow the ultraviolet patterns on flower petals with compound eyes, and communicate complex directions to their hive mates through dance. We cannot fathom what it is like to be a bee, but by studying their anatomy, physiology, and behavior in relation to their environment and each other, we can begin to understand the unique nature of their existence. Furthermore, by studying evolution we can ask not only how, but why they live and breathe as they do.

*97% invertebrates + 1.4% fish (-1 lungfish and 1 coelacanth that started it all) + 0.1% Plethodontidae (lungless) salamanders

As a final note, everyone should read Thomas Nagel’s ‘What is it like to be a bat?‘ His essay beautifully and thoughtfully articulates the issue I raise here. Our humanness may be the single greatest barrier to our comprehension of other creatures. It’s difficult, but not impossible to transcend those boundaries with diligent, thoughtful, and creative science.

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