Thorn Trees, Avocados, and VLS's (Very Large Sloths)

Photo by Greg Hume, Wikimedia Commons

This weekend I went for a walk with two of my friends through a swamp outside New Orleans. We saw plenty of waterbirds, three young alligators, some burly swamp rabbits, and a total of seven snakes. But what impressed my companions most was a honey locust tree we came across. Those are fairly common where I'm from in Arkansas, but they aren't common here, and they had never seen one before. Hearing them talk about it, I started seeing it with new eyes. The honey locust really is a stunning tree, with its clusters of icepick-sized thorns along its limbs and trunk. It's clearly not a tree to be trifled with.

Then my friends asked a question that I had never thought to ask: why does need such huge thorns? What assailant is it protecting itself from? Is it just paranoid?

None of us had any ideas, so we kept walking and forgot about it. But the next night, in one of those weird little jolts of serendipity, I stumbled across a possible answer. I was leafing through a picture book about natural history, and saw the following passage in the section on plants: "Species with fleshy fruits use animals to disperse their seeds: many of them are swallowed whole and then scattered by birds. In prehistoric times, wild avocados may have been dispersed by giant ground sloths."

That's right, giant ground sloths. They really existed. One of the most jaw-dropping things I have ever seen is a skeleton of one of these in the Smithsonian. I had seen the dinosaurs and pterodactyls skeletons and been duly impressed, but then, in the Ice Age hall, I came across the towering skeleton of Eremotherium; one of the largest of the ground sloths. The thing is just gigantic--as big as an elephant standing on its hind legs. You could build a small tree house between its pelvis and its ribcage...and it's a sloth. I stood there and stared at it like I was three years old.

Photo by Postdlf, Wikimedia Commons

Ground sloths were superficially built like long-armed bears, and like bears, they could stand on their hind legs. Some of them could reach nearly 20 feet into the trees to browse on buds, leaves, and fruit. And some of these fruits may have co-evolved with ground sloths and other big ice age mammals, as a way to disperse their seeds.

Plants can do many things, but what they can't usually do is get up and move around. That means they have to find ways to reproduce while being stuck in the same spot all their lives. They have to get their pollen to each other somehow, and then they have to scatter their seeds so that their offspring won't grow up right on top of them. Pollen is mostly spread by the wind, or by bribing or tricking flying animals like insects, hummingbirds, and bats.

Plants scatter their seeds in equally inventive ways. Dandelions and cottonwoods send them aloft on little cottony parachutes. Maple and sycamore seeds whirl like helicopter blades as the wind catches them, and the Javan cucumber's seed has wings like a hang glider. The seeds we call burs hitch rides on animals, and on our pant legs. Coconuts disperse by floating in the sea, sometimes drifting hundreds of miles from their parent plant. Some fruits dry up and explode. Impatiens are a familiar example--their fruit may burst if you touch it, which is why they are also called Touch-Me-Nots. But even more impressive is the Sandbox Tree, AKA the Dynamite Tree. Its fruits explode with a deafening blast, launching seeds over 150 feet away.

Of course, many fruits have evolved to entice animals to eat them. Plants don't put all that energy into producing sweet, tasty fruit because they have benevolent spirits. They do it to spread their seeds. Some seeds can't even germinate unless they've been through the gut of an animal. This often weakens their tough coating, and as a bonus, the seeds end their intestinal journey in a little dollop of fertilizer on the ground.

And that brings us back to avocados. Avocado seeds are too big for most modern creatures to swallow regularly, but huge prehistoric creatures like ground sloths might have gulped them down without even thinking about it, and then deposited them later in their poop, the way birds deposit blackberry seeds. Today, the ground sloths are gone, and avocados might have dwindled away too if people hadn't come along and started cultivating them. Perhaps that's only fair, since we may be what killed off the ground sloths in the first place, along with a host of other Pleistocene creatures of the Americas, including giant bison, mammoths, mastodons, and four-tusked gompotheres; as well as the predators who relied on them--massive dire wolves, sabertoothed cats, and 1800-pound short-faced bears. The fauna of the Americas was as impressive as the African savanna until a few thousand years ago--right around the time the first humans seem to have arrived. Of course, the climate got a lot warmer at the same time, so the jury hasn't declared humans guilty beyond a reasonable doubt. But they're eyeing us pretty suspiciously.

Anyway, it may be that avocados weren't the only plants left without partners by the extinction of the big mammals. Another tree I grew up around, the Osage orange, may have co-evolved with mammoths, mastodons, and their relatives. These trees once had a wide range across North America, but today they are confined mostly to Texas, Oklahoma, and Arkansas. Some biologists think this may be because their giant dispersers disappeared. In most places, Osage orange fruits simply pile up and rot under the tree. Most modern native animals ignore them, but horses eat and distribute them now. That has a certain symmetry, since Osage oranges would have evolved with native horses of the Americas, which went extinct at the end of the ice age. The reintroduction of horses from Europe may have reintroduced two old friends.

And what about the honey locust, with its menacing spikes? It's another tree that may have co-evolved with giant mammals. As prickly as it is, it's called the honey locust for good reason--its seed pods are filled with a sweet-tasting pulp that probably evolved to attract large animals, who would eat the seeds along with the pulp. If the seed pods aren't eaten, they just fall to the ground, and the seeds inside will be destroyed by insects. But if they get eaten by a large herbivore, they will pass through its gut unharmed. This is actually what happens with relatives of the honey locusts in Africa, the acacias. Elephants help disperse some acacia seeds by eating the pods. The insects attacking the seeds are killed, but the seeds do just fine; and are actually much more likely to germinate if they've made a trip through pachyderm innards. But elephants and other large mammals can be hard on acacias, too--stripping their bark, pushing them over, and browsing too many of their leaves. That's why acacias have thorns--to deter this sort of thing. Their cousins, honey locusts, have even bigger thorns. And maybe that's the answer to my friends' question. Why does that tree we looked at just this weekend have such huge thorns? Maybe it's still trying to protect itself from giant creatures that disappeared thousands of years ago. Those great beasts may seem almost mythical to us, but they were very real, and museums are full of the bones to prove it. They were certainly real to the honey locust, and it still has its thorny daggers ready, in case they ever return.

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Anachronistic Fruits and the Ghosts Who Haunt Them / Connie Barlowe

The Trees that Miss the Mammoths / Whit Bronaugh

Saving the Seeds (David Attenborough clip on acacias and elephants)

Endless Forms Most Wonderful

It's time, as the old song says, to accentuate the positive. My last couple of posts took a pretty jaundiced view of the living world, focusing on some of its more ghastly creatures. They're out there, but I don't want to dwell on them too much. Nature has produced plenty of wonder and beauty, too. What's most wondrous to me is the diversity of life--the amazing variety of ways to be a living organism. There are nine-pound crabs that climb trees but can't swim, and spiders that live their whole lives under water, wearing a web-bubble full of air. Bacteria flourish under Antarctic ice, and algae turn snowfields pink high in the mountains. In 1995, scientists found a creature that lives only on the mouth bristles of lobsters. I'm convinced you could study life on Earth for a thousand years and and never run out of surprises.

Life has been evolving for at least 3.5 billion years, creating millions of different species, each with its own unique--and often completely astounding--way of getting by in the world. The best estimates put the number of species on Earth today at around 8.7 million, and the ones living today are just a small percentage of all the species that have ever lived. The earth has seen entire dynasties of living organisms rise, diversify for tens of millions of years, and finally go extinct.

Our species, then, is a single living branch on an ancient tree; one of mllions of other branches. Before I talk about some of the weirder branches, it's worth mentioning a couple of things about the tree's major limbs, because our understanding of those has changed a lot in the last 50 years or so. There's still a lot of misunderstanding out there--lots of people still think you can classify every living thing as a plant, an animal, or a microbe. It's not that simple.

Early taxonomists like Linnaeus classified the natural world into three kingdoms: animal, vegetable, and mineral. Linnaeus classified living things using a hierarchy of categories (kingdom, phylum, class, etc.). One kingdom includes multiple phyla, which themselves include multiple classes, and so on. This system can be represented as a branching tree, but Linnaeus lived before Darwin, so he thought of it more as an organizational chart than a genealogical tree. In the mid-1800's, though, scientists started thinking of living things changing and diversifying over time, and Darwin explained the basic mechanism by which that happened. The tree of life turned out to be a true family tree.

The more biologists learned about the tree of life, the more complex it got. Microscopic organisms were given their own kingdom, Protista, as in this 1866 diagram by Ernst Haeckel. Then people realized that life has even broader divisions than kingdoms. Two of the deepest branches in its tree are between prokaryotes--simple cells with no nucleus, like bacteria--and eukaryotes, whose cells are more complex, and nucleated. Then prokaryotes themselves were found to contain two distinct groups: bacteria, and another kind of microscopic organism called archaea. Fungi turned out not to be a kind of plant, but an entirely separate kingdom, more closely related to animals. 

Today, most biologists divide the tree of life into three domains: Bacteria, Archaea, and Eukaryotes, as in the tree below. Each of these domains has deep divisions that correpond to kingdoms. Animals, plants, and fungi are still considered kingdoms within the eukaryotes, but so are other groups of eukaryotes. Single-celled eukaryotes like amoebas, giardia, and euglena are informally referred to as protists, but that's just a term of convenience, not a real biological group. Some non-animal/plant/fungi eukaryotes, like kelp, are multicellular and big enough to form underwater forests.

From Wikipedia

Now let's get into the fun stuff--the amazing diversity of lifestyles in nature. As animals, we get our energy and basic building blocks (organic molecules) by eating other organisms. Plants, of course, make their living in a totally different way. They get energy from the sun, and then use it to assemble their own organic molecules from scratch. Most people figure that since plants grow out of the dirt, they must be made of dirt. But they aren't. Soil just provides minerals and other nutrients. If you weigh the soil in a pot, then grow a five pound plant in it, and then weigh the soil again, you won't find much difference before and after. Plants literally build themselves out of air and water, using sunlight. Carbon dioxide in the air provides the carbon that forms the backbone of organic molecules. This trick, of course, is called photosynthesis, and it makes life possible for most living things--even the ones, like us, who can't do it. But plants didn't invent photosynthesis. Bacteria learned it long before plants existed, and so did many single-celled protists (some of which hedge their bets and eat other organisms too). 

Some bacteria and archaea get by in more exotic ways. Many can build their own organic molecules without light, using energy from chemicals like sulfur, iron, and even ammonia. Some of these weird organisms support ecosystems that grow in total darkness, around boiling volcanic vents at the bottom of the sea. There they form symbiotic relationships with seven foot tubeworms, who shelter them inside their bodies. Not how I would want to live, but it works for them.

Unexpected symbioses like that are common. Lichens are a symbiotic amalgam of algae and fungus. Termites and cows rely on bacteria in their guts to digest cellulose. Figs need tiny wasps inside their fruits in order to reproduce, which is why some vegans and squeamish biology majors won't eat figs. The bobtail squid of Hawaii harbors symbiotic bacteria that allow it to glow in the dark. Kudzu, soybeans, and alders develop nodules on their roots to house bacteria that help them use nitrogren. 

In plants and protists, photosynthesis itself is based on an ancient symbiosis. Chloroplasts, the photosynthetic cellular organs inside their cells, originated as bacteria that took up residence inside other organisms. Sometimes this process happened twice. For example, red agae is a kind of seaweed that isn't related to plants. Once upon a time, a single-celled ancestor of red algae engulfed photosynthetic bacteria and gained the ability to photosynthesize. Later, other eukaryotes called chromealveolates engulfed the red algae cells, creating a double-layer of internal symbiosis. They went on to form a major lineage of eukaryotes, which include several kinds of algae, as well as kelp, diatoms, and the parasites that cause malaria. It's a family with diverse interests. The red algae, meanwhile, formed several multicellular lineages, some of which get hardened with calcium and build reefs alongside corals (which are colonial animals).

It's a strange, unexpected world out there. Think of the amazing variety just among the plants. There are plants in the desert called living stones that avoid herbivores by looking like rocks. Here in Louisiana I see resurrection ferns along the limbs of live oak trees. They get their name because they look stone dead when it's dry, but then they have a green resurrection as soon as it rains. The titan arum of Sumatra produces a flower that can be ten feet tall. It's pollinated by flesh flies and carrion beatles, which is why it smells like something crawled into it and died. 

Plants have been co-evolving with insects for millions of years, forming some truly astounding relationships. Bee orchids get pollinated by tricking bees into trying to have sex with their flowers. Spider orchids trick wasps into stinging them. Darwin's orchid, like many flowering plants, bribes insects with nectar. But it keeps it at the bottom of a tube that can be over ten inches long. When Darwin saw it, he predicted that a moth would be found with a 10-inch proboscis, long enough to reach the nectar. The moth was discovered years later, after Darwin was dead.

The organisms that most capture the human imagination are our fellow animals. They're a stunningly diverse bunch, from lowly sponges and hideous tapeworms to lions, tigers, and bears. Animals have some strange lifestyles and behaviors themselves. There are male jumping spiders that flare their backsides like peacocks and wave their arms in the air to woo females. Scallops, which look like flattened clams, can swim away from predators by flapping the two halves of their shell together. Water beetles breathe through their rear ends (and some turtles can do the same thing). The boxer crab, also known as the pom-pom crab, is so-named because it holds a tiny, stinging sea anemone in each of its pincers. When threatened, it gives its opponent an anemone sandwich. Sometimes nature is dowright hilarious.

Our own group of animals, the vertebrates, is also full of surprises. Consider the world of fish. The first surprising thing about them is that they aren't a coherent biological category. Cartilaginous fish like sharks and rays are very different from bony fish like catfish or bass, and those, in turn, are different from lobe-finned fish like coelacanths (famous "living fossils") or lungfish. Lobe-finned fish were the ancestors of four-legged vertebrates, which means a lungfish is more closely related to us than it is to a shark. 

Fish have been around long enough to evolve into some truly weird forms. The gulper eel is basically a giant set of jaws with a tail, and it can swallow things much larger than itself. The tip of its tail glows, too, in case it wasn't freaky enough already. The eyelight fish, one of several kinds of flashlight fish, has bioluminescent lights under each eye. The barreleye has eyes on barrel-shaped stalks, enclosed inside a transparent dome on its head. The deep sea anglerfish is famous for the glowing lure that hangs from its forehead, and for being butt ugly. But the weirdest thing about it is its sex life. Male anglerfish are tiny, and when they find a female they attach themselves to her permanently, and then sort of dissolve on the inside, basically becoming a bag of gonads. Some females have five or six of these dangling off of them. Who says romance is dead?  

Then there's the flying fish, famous for leaping out of the water and gliding for hundreds of feet on wing-like fins. This is so well-known it's easy to forget how odd it is--this is a fish we're talking about here. But gliding isn't unusual among vertebrates. It's evolved several times. Wallace's flying frog flares out its fingers and toes and glides on the membranes in between. Flying lizards flare out their ribcages as wings. Flying snakes flatten their bodies, launch themselves out of trees, and glide by slithering through the air. Among the mammals are the flying lemurs and flying squirrels. They both glide with flaps of skin between their front and back legs, but they aren't closely related, which means their abilities evolved separately. Gliding must be a handy trick.

Gliding is just one of many weird, wonderful traits among animals. Possibly the most amazing of all, for my money, is this: baleen whales--the largest animals that ever lived--have an expandable mouth, like a pelican. They can hold more than their weight in water in their mouth...and some of them weigh nearly 200 tons. They take in all that water, strain krill out of it, and spit it out again. These behemoths are out there doing that right now, in oceans around the world. 

That kind of fact boggles my mind. But it's just one of many such facts about animals. And animals are just a part of a huge, diverse tree of life, and even life is just one aspect of the natural world. It's easy to get carried away talking about all the wonders of nature, and that's just what I've done in this long, rambling post. I can't help it. It's an astonishing world out there.

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The frog and tree pictures above are both by the German biologist Ernst Haeckel. If you haven't seen his natural history illustations, I urge you to check them out. 

The Lord God Made Them...All?

Peaceable Kingdom, Edward Hicks 1834

I've always loved James Herriot's books about his life as a Yorkshire veterinarian. That was pretty much inevitable, since I'm the son of an English teacher and a rural veterinarian. The books are full of comical but kind-hearted stories about eccentric creatures and their even more eccentric owners, and they're pretty much delightful all the way through. If you find yourself in a bad mood, Dr. Herriot offers good medicine.

The title of one of his books, which is often used as the title of the whole set, is All Creatures Great and Small. This comes from the second line of an Anglican hymn called Maker of Heaven and Earth, written by Ms. Cecil Frances Alexander in the 1840's. Its first verse goes:

All things bright and beautiful,
All creatures great and small,
All things wise and wonderful,
The Lord God made them all.

Once Herriot had used the second line, it was a no-brainer to use the other three for the titles of later books. I always liked those four lines. They really do fit the books perfectly, with their unabashed innocence and reverence. They don't match the more cynical, ironic aesthetic you find these days at all, but that's fine with me. 

But the rest of the hymn, it turns out, isn't as charming. Besides getting a bit too cutesy, it also includes this uncomfortable little verse: 

The rich man in his castle,
The poor man at his gate,
God made them high and lowly,
And ordered their estate.

Yikes.

That's not the only part of the hymn I can't agree with, though. As much as I like the first verse, I don't think the Lord God really made them all, any more than I think he made the 19th century English class system. Science has made it clear that all the animals on earth, as well as all the plants, fungi, diatoms, bacteria, etc, were shaped by evolution, not God. If there is a God, maybe he set the whole thing in motion, but even if the theory of evolution had never been formulated, I still wouldn't believe God could have crafted each of the living things on earth himself. Not if God is good, as most theists think he is.

Because the thing is, all things aren't bright and beautiful, much less wise and wonderful. Some creatures are really just horrid. I learned this at an early age, because as I said, my dad is a veterinarian. For as long as I can remember, he's had a jar in his office with a dog's heart in formaldehyde. The dog was killed by the heartworms that are still packed into its heart like a fistfull of vermicelli. Dad brings it out to show people why they need to get their dog on heartworm prevention medicine. It works. He's also got a jar of sheep bot fly larvae, and the less said about their life cycle, the better. Suffice it say you don't want to be a sheep.

When people wax eloquent about how God crafted all creatures great and small, they don't usually have heartworms or bot flies in mind. They talk about lambs, or hummingbirds, or whales...the beautiful people of the animal kingdom. But really, those who believe there's a God, and that he is good, might want to think twice about crediting him with some of the other creatures. Did God create the heartworm as well as the lamb? Did he create the bot fly that lays its eggs in that lamb's nose (sorry, TMI). Did he create the brain-eating amoeba and the bubonic plague...or the fleas that carried it...or the rats that carried them? Did he devise the lifecycle of the parasitic wasps I discussed in my last post? Did he teach the little cuckoos, laid in another bird's nest, to hatch early and push the rightful eggs over the edge? Do we really want to chalk those things up to God? 

The irreverent geniuses of Monty Python made the same point, lampooning Ms. Alexander's optimistic little hymn with their version; All Things Dull and Ugly, which begins:

All things dull and ugly
All creatures short and squat
All things rude and nasty
The Lord God made the lot 

Each little snake that poisons
Each little wasp that stings
He made their brutish venom
He made their horrid wings

Now, some may think I'm doing a sort of reverse cherry-picking, by choosing some especially yucky creatures to talk about. Surely those are in the minority? Well, no. Most people think parasites are on the yucky side of creation, and if you include bacteria and viruses in the definition of "parasite", then parasites may outnumber "free-living species" four to one. Parasites strike us as especially uncalled for, but they aren't the only source of nastiness in the living world. Male ducks, for example, practice something euphemistically known as "forced copulation". Among mammals, infanticide is rampant. There are snakes that lie in wait in nests, and welcome hatching babies into the world by eating them. They've been doing this since the hatchlings were dinosaurs. Most species on earth either eat, or are eaten by, other species. Many do both, of course (though they tend to have the second experience only once). 

If God is good, and God made the natural world--designing each organism in its turn--why is there so much pain and strife in nature? If you're going to credit a supernatural creator, Satan seems like a better candidate than God for some of what goes on out there. Doesn't Old Scratch seem more likely, for example, to have arranged for baby sharks to eat each other in the womb? That has his stamp all over it. As Darwin himself said, "What a book a devil's chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel work of nature!"

You can believe that God is good, or you can believe that He created every species personally, but I don't see how you can believe both at the same time. This leads to a surprising thought. If you want to keep believing God is good, it actually makes more sense to believe living species were created by a blind, amoral process of natural selection than individually by God. Natural selection is where all the evidence points, anyway, and it doesn't put us in the position of trying to explain why God made the liver fluke and the Guinea worm. Or, for that matter, why Satan did. The idea that those things evolved by blind natural processes may not be especially uplifting, but it's not as depressing as thinking they were created by a vengeful God or the evil king of the underworld.

But enough about the nastiness of the living world. It is an undeniable fact, but there's a lot more to nature than that. As shocked as Darwin was by waste and cruelty in nature, he also found nature awe-inspiring. This is apparent in these beautiful and oft-quoted concluding lines of The Origin of Species: 

Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

In later editions of the book, Darwin actually changed the text to say "breathed by the Creator." I'm not sure whether he believed this, or if it was meant to make the idea more palatable to the public. Darwin himself seems to have been an agnostic later in life. Whatever the implications of his theory for religion, Darwin was right about evolution, and I think he was also right about nature's grandeur. It really is full of "endless forms most beautiful and most wonderful". Nature may be amoral, but it's astonishingly creative; inventive beyond all human imagining. Some of those creations are beautiful, and some are awful, but all of them are amazing in one way or another.

From salt-loving bacteria in boiling volcanic pools, to horned narwals navigating though arctic ice, the variety of life is stunning. This world has seen dragonflies the size of crows and giant ground sloths the size of elephants. There are fish that fly and birds that swim; flowers that mimic insects and insects that mimic flowers. In the Rocky Mountains there are aspen groves--single organisms connected at the roots--covering dozens of acres and living for tens of thousands of years. You could study the living world all your life and never run out of wonders to marvel at. The Lord God didn't make them all (and that should be good news for people of faith), but that doesn't mean the world can't be bright and beautiful.

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Do Parasites Rule the World? / Carl Zimmer

I discovered Monty Python's version of the hymn, and Darwin's remarks about a devil's chaplain, in Richard Dawkins' excellent book The Greatest Show On Earth.

Rough Beasts

I have an odd habit. I'm always watching for interesting flowers and insects, taking pictures of them, and posting them on Facebook--as if everybody thought they were just as fascinating as I do. And sometimes they do. The other day, a friend (who, unlike me, actually makes a living as a writer) suggested I write about some of the weird bugs I see. It seemed like a good suggestion. I've let myself get too preachy on this blog anyway, and besides, she's a professional and I should probably listen to her.

The only problem, though, is that if you look closely at the world of insects, what you see tends to be kind of horrifying. As Annie Dillard put it, "Fish gotta swim, birds gotta fly; insects, it seems, gotta do one horrible thing after another."

It's true. Insect behavior can remind nature lovers like me not to romanticize the natural world too much. Nature can be achingly beautiful, but it's also for the most part amoral. It's not cruel--cruelty requires consciousness--it's just blind to things like hope, pleasure and pain. In the poem The Second Coming, Yeats talked about a "rough beast...its gaze blank and pitiless as the sun." Most of the time, nature is just such a beast.

Sometimes it seems the like littler nature's beasts are, the rougher they get. For example, the other day I spotted this little drama on a blade of grass. A katydid was in the grip of Sphex nudus, the Katydid Wasp. In the picture it looks like the katydid is about the become the wasp's dinner, but actually...it's worse than that. Digger wasps like Sphex nudus sting their prey to paralyze them, and then bring them back to their nests, which are burrows in the ground. Then they deposit them in one section of the nest, lay an egg, and seal the chamber up. When the egg hatches, the larva will feed on its living larder. The wasps are parasites (parasitoids, technically, but we won't get into that).

This katydid may have escaped that fate, because the wasp got alarmed by my camera and dropped it. I like to think the katydid hadn't been stung yet, and that the wasp didn't come back. But I don't know. I also like to think katydids are absolute automatons, as incapable of conscious experiences like pain and fear as a wind-up toy robot. At least I hope that's true of the ones that run into Katydid Wasps. But I don't know that either, and I suspect it's not entirely true. And evolution doesn't care either way. If evolution is blind to pleasure and pain, then behaviors like this will evolve whether or not the victims are conscious of what's happening to them.

And evolve they do, over and over again. Among the Katydid Wasp's cousins are the similarly thread-waisted Mud Daubers. We called these Dirt Daubers where I grew up in Arkansas, and in my family they were considered the good guys of waspdom, because they almost never sting. Well, they almost never sting people. They do sting spiders, for the same reason Katydid Wasps sting katydids. Mud daubers build their little adobe nests and give each larva its own compartment, well-stocked with several paralyzed spiders for it to dine on. The Blue Mud Dauber's young mostly eat Black Widows. How's that for tough?

I discovered the "good guy" mud dauber's dark secret for myself as a kid, when my mom had me knocking old mud dauber nests off the ceiling of our porch. I broke one open out of curiousity, and dead spiders cascaded down my arm, as I did lively little dance of terror. Maybe is was the Tarantella.

Whatever their secrets, mud daubers have enemies of their own, and some of them are other wasps. I encountered one of these a couple of years ago. I heard a constant buzzing sound at my back door, and when I went outside to look, I found a mud dauber nest on the screen. On it was a little iridescent wasp, so pretty it could have been made by Carl Fabergé, busily chewing its way inside. That seemed a little odd to me, so I went back inside and looked it up. It turned out to be a Cuckoo Wasp, and like its avian namesake, it's a brood parasite--it lays its eggs in the nests of others. When the Cuckoo Wasp larva hatches it proceeds to eat the Mud Dauber larva, as well as its paralyzed guests. Naturally, the mother Mud Dauber doesn't appreciate that, and it will attack the Cuckoo Wasp if it catches it. But the Cuckoo Wasp is ready. Its jewel-like exoskeleton is armored, and it just rolls itself up into a defensive ball like an armadillo. The proprietor of the nest usually can't do much but pick it and bounce it from the nest. Whereupon it simply unrolls and tries again. The Cuckoo Wasp is a tiny little reflection of nature itself: gorgeous and amoral.

Life isn't easy, even for wasps tough enough to feed their babies paralyzed spiders. Sometimes it's downright embarrassing (or would be if wasps had the brains to be embarrassed). Like many insects, spider-hunting wasps can be fooled by an organism with no brain at all--an orchid. Most people have heard how some orchids mimic female bees or wasps. The haplessly horny males try to mate with the orchid, and end up with packets of pollen stuck to their bodies. But they don't learn from their mistake, so they deposit the pollen on the next orchid they try to get cozy with. It's probably a good thing orchid flowers aren't as big as humans, because some guys would probably pollinate them, and just imagine what those flowers would look like.

Moving on...Spider Orchids of the genus Brassia use a slightly different tactic. They really do look like spiders, at least enough to fool certain wasps. The wasps land on the flowers and start stinging them, trying to paralyze the "spider". The only result is that they get a bit of pollen attached to their heads, which they will deposit on the next "spider". The orchids get pollinated, and the wasps get nothing.

But not all plants are so hard on the parasitic wasps. The cabbage plant, for example, is their ally. The caterpillars of the Cabbage White Butterfly, as their name implies, like to eat cabbage. But the cabbage doesn't like--in an unconscious evolutionary sense--to be eaten. When it starts to get munched it releases a chemical that attracts parasitic wasps which attack the caterpillar. But they don't take it back to their nest. Instead, they lay their eggs inside the caterpillar, which goes about its business. The wasp larvae hatch and begin to grow inside it, feeding on its fluids but avoiding its vital organs. Finally, they tunnel out of the caterpillar's side and start spinning cocoons for themselves.

And then, as if this tale weren't perverse enough, things start to really get crazy. The caterpillar's brain has been altered by its ordeal, and it actually helps encase the wasp larvae in a mass cocoon, using its own silk. And then, then it becomes their guard caterpillar. The wasp larvae are vulnerable to attack by other parasitic wasps, which lay their eggs in them. The addled caterpillar lashes out at them when they try, but it's understandably weak by now, and soon dies. Many of its wasp attackers get parasitized themselves by smaller wasps. And get this--those smaller parasites may become the hosts for yet another species of parasitic wasp. This is called hyperparasitism--the parasite gets parasitized. Sometimes this can keep going, for four, five, or more levels, all the way down to bacteria that are attacked by bacteriophage virues. It's like a horror story version of Johnathon Swift's poem:

"So nat'ralists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller fleas to bite 'em.
And so proceeds ad infinitum."

Ah, the web of life..it's not all peace and harmony. In fact, it can be pretty dreadful. After all, that famously disturbing scene in the movie Alien was inspired by parasitic wasps. Of the living things that can't make their own food, like plants do, parasites may be the most abundant.

But maybe things aren't as bad as they seem. Maybe none of the players in these little dramas are actually conscious, and they only appear to feel things like pain, fear, or anger. Maybe. But we can be pretty sure that other animals, like birds and mammals, do experience those sensations, and they (and we) can do some pretty awful things to each other, too.

And the thing is, nature doesn't care. It's gorgeous and complex and awe-inspiring, but it doesn't care.

That's where we, and maybe a few other animals, part ways with the rest of nature. That's the silver lining in all this. We can realize that others--both human and animal--have sensations and preferences, and we can alter our behavior to avoid to avoid causing unnecessary pain. Unlike nature, our eyes are not blank and we don't have to be as pitiless as the sun...or a wasp.

In the movie The African Queen, a drunk Humphrey Bogart tells a prim Katherine Hepburn, "A man takes a drop too much every once in a while. It's human nature." She replies, "Nature...is what we are put in this world to rise above." I don't know what we were put in this world for, if anything, and I think she could give nature a good bit more credit. But she's still got a point. As amazing as nature is, when it comes to things like compassion and ethics, we actually can rise above it.

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Enter the Hyperparasite

National Geographic video about the White Cabbabe Butterfly being parasitized. Watch at own risk. No, seriously--it can't be unseen.

Pilgrim at Tinker Creek / Annie Dillard (possibly the most brilliant book I've ever read)

The Cuckoo Wasp: A Gorgeous Parasite

National Geographic Article Mentioning Spider Orchids