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  • 5/19/2025
Mites, beetles and borers that share man's surroundings are observed in this look at microscopic intruders including bacteria, viruses and fungi.

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00:00Tonight on NOVA, bloody battles, sinister traps,
00:07micro-photography reveals hundreds of hidden worlds teeming with life.
00:14But wait, what is this mysterious creature?
00:17You know them better than you think.
00:19Crawling on your clothing, pulling on your hair, even snacking on your skin.
00:25Odyssey of Life continues with The Unknown World.
00:42NOVA is funded by Prudential.
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01:02And by Merck.
01:06Merck, pharmaceutical research.
01:09Dedicated to preventing disease and improving health.
01:15Merck, committed to bringing out the best in medicine.
01:20The Corporation for Public Broadcasting and viewers like you.
01:35There is a world unknown to most of us.
01:38It exists side by side with our own.
01:42A world of radically different perspectives, where a drop of water can be home.
01:50Those who live here eat the books we prize,
01:54devour our plants, stalk each other without mercy.
02:01They even stalk us through the strange and eerie landscapes of our bodies.
02:10Tiny monsters revealed by special optics and micro-photography.
02:16Our next door neighbors.
02:19The stuff of nightmares, if we dare to look.
02:29In their world, even a head is unfamiliar terrain.
02:39And the palm of a hand is like a furrowed field.
02:49This unknown world is just too small for us to take notice.
02:55We see only our world, built on our scale.
02:58Large, open and familiar.
03:04We don't even know what we're missing.
03:10In the unknown world, our chest hair is the only thing we see.
03:18This is an overgrown jungle.
03:23Our scalp is a tropical rainforest.
03:36And here are the fertile hillsides of the forearm.
03:44The desolate desert of the inside of the wrist.
03:49The vast wasteland of the sole of the foot.
03:58The vast wasteland of the sole of the foot.
04:07The body we think we know is really an illusion,
04:11born of our limited perspective.
04:15Sometimes, of course, ignorance is bliss.
04:19It's not easy accepting the fact that billions of other organisms live on and in us.
04:28Most of them are bacteria like these.
04:35A microscopic swarm in a drop of sweat.
04:39Some of our closest companions have never been introduced to us.
04:46The hair follicle mite lives in holes in our scalp through which hair grows.
04:52A kind of tiny, parasitic mole.
05:08It looks like a science fiction creature, but it's only 1,250th of an inch long.
05:21That's small enough to escape the attention of our nerve cells.
05:26Otherwise, we'd never stop scratching.
05:30Just knowing they exist is bad enough.
05:38The mites especially like the large follicles of our eyelashes.
05:46They thrive on fat and dirt and have even developed a taste for mascara.
06:00But for other denizens of the unknown world,
06:04there's a much more abundant food source nearby.
06:12It's our skin, constantly renewed by new cells pushing up older ones.
06:18The top layer is made up of dead, compacted cells.
06:23Every hour, we shed one and a half million skin flakes.
06:29And each one has its own colony of hitchhiking bacteria.
06:40The air is full of these small pieces of ourselves
06:44and the microorganisms that call them home.
06:48What we see in the mirror is a layer of dead cells soon to be cast off.
06:54Still, even dead cells have their appeal.
06:58How do I look?
07:02Absolutely beautiful.
07:05But change the perspective, and it's a different story.
07:16When we're finally forced to face reality,
07:19we find that dead skin makes up 90% of the dead cells in our body.
07:25And it's not just our skin.
07:27It's the skin of our entire body.
07:30When we're forced to face reality,
07:32we find that dead skin makes up 90% of the dust on our floors,
07:37not to mention an army of creeping, crawling creatures.
07:44This is the front end of a dust mite, seen through an electron microscope.
07:51It's about an 80th of an inch long, impossible to see with the naked eye.
08:01It's diet is mostly skin flakes, and there are more than enough to go around.
08:08It's a never-ending feast, and we're the purveyors, like it or not.
08:18Dust mites are everywhere we are.
08:22Here we see one of them enjoying his dinner,
08:25although his table manners could use a bit of improvement.
08:30Clearly, his parents never cautioned him against playing with his food.
08:43If you think you can get away from dust mites,
08:46you're wrong.
08:49If you think you can get away from dust mites, think again.
08:53Even in our beds, they keep us company.
08:58They move easily through the weave of blankets and sheets,
09:02in search of more food.
09:07They scavenge when we're awake, and when we're asleep.
09:12They are insatiable.
09:15But why not go to the source itself, our own skin?
09:21Food is everywhere, waiting to be harvested.
09:28But before you run to take a shower, consider this.
09:32Dust mites are really sanitation workers, who help clean up our mess.
09:37Mites play an essential role in the ecological process,
09:41turning our biological waste into their food.
09:52So, when we eat breakfast, they eat breakfast too.
09:57In fact, for every source of food,
10:00there's a group of hungry organisms scanning the menu.
10:06If we're not the specialty of the house, then something else will be.
10:10This may look like a closet,
10:12but it's really a restaurant for insect gourmets.
10:17You can tell if they really like an entree,
10:20by the horrible smell of their food.
10:25The smell of the food is so strong,
10:28that it's hard to tell if it's a meal or a snack.
10:34The smell of the food is so strong,
10:37you can tell if they really like an entree by the holes.
10:45These small white larvae of the common clothes moth
10:49are especially fond of wool and fur.
11:07When they're fully mature, these well-fed larvae will reach the final stage of their development,
11:12becoming moths who will produce the next hungry generation.
11:26But wool and cotton aren't the only things on the menu.
11:30There's also a tasty fur coat, which the fur beetle swears by.
11:38It lives deep within the fibers of the coat, and it lays its eggs there.
11:50For the yellowish-brown larvae that hatch,
11:53home is also breakfast, lunch, and dinner.
12:08They move using three pairs of legs and their jointed bodies.
12:19Between their eyes are powerful jaws that can saw off the hairs of the fur,
12:25as their legs grip them securely.
12:38Fur beetles are discreet animals, whom we seldom see.
12:49We only know they're here when we see their handiwork,
12:53especially when their favorite meal is a favorite dress.
12:58But there's no point in taking it personally.
13:01Like us, they eat to survive.
13:11Even in our prestigious halls of learning,
13:14there's a legion of ravenous creatures that live here.
13:19Even in our prestigious halls of learning,
13:22there's a legion of ravenous creatures waiting for us to turn our backs.
13:35No door, no lock can keep them out.
13:40When we leave at the end of our day, their day begins.
13:46To these creatures, precious books are nothing but dead wood,
13:50no different from a stump or fallen branch.
13:56The subjects are irrelevant,
13:58the fine leather binding is just more organic material,
14:02and they're not even interested in us.
14:10Material to break down and recycle.
14:16You wouldn't know it from looking at them,
14:18but silverfish have an ancient pedigree.
14:21They haven't changed much in 500 million years.
14:27They grow to about a third of an inch long,
14:29and prefer old, yellowed paper.
14:33With the help of an enzyme,
14:35they break down the cellulose in paper into food.
14:48Unfortunately, they're quite illiterate,
14:51and make no distinction between Hamlet and yesterday's newspaper.
14:56They like them both equally.
15:09The printed page has a number of aficionados in the insect world,
15:14including the pseudoscorpion,
15:16a miniature predator always on the prowl.
15:20It lives on a diet of book lice, another lover of paper.
15:26The louse is killed by poison, secreted by the scorpion's claws.
15:39The scorpion is the only creature in the world
15:42that has ever been able to eat paper.
15:46Then the scorpion is off to the next victim,
15:49wherever it may be browsing.
15:58Our finest museums also have an unknown world of hungry organisms,
16:03and they're everywhere, even if we never see them.
16:10Their victims can do nothing but stare at us,
16:13their victims can do nothing but stare at us reproachfully.
16:18Mighty once, they are helpless now.
16:25Imagine the indignity of it.
16:27In every museum of natural history,
16:30stuffed animals, long dead, are food for the living.
16:37In the lion's fur, hidden from sight,
16:40the microscopic museum beetle is busy,
16:43admiring the taxidermist's art.
16:49The museum beetle is a close relative of the fur beetle,
16:53with similar tastes, but only half the size.
16:59It loves the protein in hair and feathers,
17:02and relishes fat and dirt.
17:06It eats, delicately, one hair at a time.
17:15But in the long run, it's the scourge of every curator.
17:36The museum beetle doesn't limit itself to stuffed lions.
17:40Instead, it savors all sorts of collections.
17:47Dried insects are a prime target.
17:55The museum beetle has no respect for science.
17:58A rare specimen is just another snack.
18:06A collection that took decades to assemble
18:10can be ravaged in days.
18:15Not that most of these specimens wouldn't have done the same,
18:19given the chance.
18:29But there's more here to eat than just dead animals.
18:33There's also a vast quantity of other organic material.
18:41The exhibition cases are framed with wood.
18:45And wood can be food, or shelter, or both,
18:49to a wide range of organisms.
18:56The holes signal the presence of an army of tiny wood-eaters.
19:03Beneath the surface, you can find an endless system of tunnels
19:07and the creatures that make them.
19:19The white larvae of the old house borer
19:22will stick around as long as there's wood to gnaw.
19:34This is the old house borer's colleague, the carpenter ant,
19:38for whom wood isn't food, but shelter.
19:46It tunnels through the wood to make its nest.
19:51Then it carries away the chewed wood,
19:54leaving space in which to live.
20:04The result is wood destruction.
20:07It's not food, it's not shelter.
20:10It's not food, it's not shelter.
20:14The result is wood destroyed from within,
20:18business as usual in the cycle of life and death.
20:35Nothing is safe in the unknown world.
20:40Even our own bloodstream can be a highway for invaders.
20:48But that doesn't mean we have no defenses.
20:51Within seconds of a cut,
20:54a net of threads called fibrin slows the loss of blood.
21:00The net forms when a substance in the torn skin
21:04reacts with another substance in the blood.
21:08The blood coagulates with a kind of natural glue.
21:19The blood is a natural glue.
21:22The blood is a natural glue.
21:30The blood is a natural glue.
21:44The glue then forms a scab,
21:47which covers the wound until the skin can heal itself.
21:55Skin cells divide again and again
21:58to form the first layer of new skin beneath the scab.
22:13Other layers are then built up from beneath.
22:18The most common invaders are bacteria,
22:22one of the simplest forms of independent life.
22:28They come in a variety of shapes and sizes.
22:38They exist practically everywhere in incredible numbers.
22:43There are 100,000 billion in a human body.
22:59Not that all bacteria are dangerous.
23:03In our intestines, they play an essential role in digestion.
23:12They combine with stomach fluids and enzymes
23:15to break down food into nutrients.
23:20This salad will need their help
23:23as it makes its way through the digestive tract.
23:28But other bacteria are long-standing enemies,
23:31like the ones that attack our teeth,
23:34causing cavities and plaque.
23:38Enzymes in our saliva usually keep them in check,
23:42but if we forget to brush, the battle may be lost.
23:48Enemy manpower is unlimited.
23:53These bacteria are moving among the cells of the mouth.
23:58Swimming down microscopic rivers in our mucous membranes.
24:13The bacteria thrive on the rough surfaces of our teeth,
24:17where a toothbrush can't reach.
24:29A single bacterium can divide itself
24:32into one million new bacteria in just eight hours.
24:37Without our defenses, we would never survive the onslaught.
24:45But each of us has billions of cells patrolling our body.
24:53An army of soldiers, often stronger than our enemies,
24:57working together on the front line.
25:04The first wave of troops are the macrophages,
25:07which literally means big eaters.
25:12Hundreds of thousands of them travel through the blood vessels
25:15and lymphatic system, ready to attack.
25:22With long, retrieving arms,
25:24they capture bacteria and kill them.
25:42Macrophages deal with invaders simply by eating them.
25:47They can tell a bacterium from a normal body cell
25:50by scanning its surface.
25:53The cell's chemical structure reveals whether it's friend or foe,
25:57to be left alone or devoured.
26:07Macrophages ultimately eat themselves to death,
26:10taking the trespassers with them.
26:17Together, millions of dead macrophages and their victims
26:21make up the substance we call pus.
26:30A macrophage will attack any foreign body it finds.
26:40Here, asbestos fibers that enter the macrophages
26:44Here, asbestos fibers that enter the bloodstream through the lungs
26:47are marked for disposal.
26:55Even another macrophage who's died in the line of duty is devoured.
27:07Our defender cells are always on patrol.
27:11But some invaders are more difficult to deal with than others.
27:16And some seem nearly impregnable.
27:29This is a virus, a tiny piece of genetic material
27:33surrounded by protein.
27:40Recreated using electron microphotography,
27:43they're visible here as blue dots on the surface of a cell,
27:47only one hundredth the size of a bacterium.
27:59Because a virus can't reproduce without a host cell,
28:03it isn't considered a living organism.
28:06But it can kill.
28:09It forces its way into the cell nucleus
28:12and programs the cell to make more viruses,
28:15copies of itself.
28:21This is a recreation of the inside of a cell.
28:24The red structures are mitochondria, the cell's power plants.
28:30The yellow balls are ribosomes, which make protein.
28:40But now, hidden among them, is an enemy factory hard at work.
28:48When the cell has made enough copies of a virus, it dies.
28:52And thousands of new viruses leave in search of new cells to invade.
28:59This is what happens when we catch a cold,
29:02and far worse diseases.
29:10A cell nucleus is seen here in the middle.
29:14Surrounding it are viruses.
29:18The smaller mitochondria are still working away,
29:22protected inside the cell membrane.
29:26But their fate is already sealed.
29:30Using a unique photographic process,
29:33we can now catch the viruses in the act of entering the cell.
29:40About 100 of them are grouped on the cell's surface.
29:44Then suddenly, as if on a given signal,
29:47they force their way into the cell nucleus.
29:50And the virus is killed.
29:53About 100 of them are grouped on the cell's surface.
29:57Then suddenly, as if on a given signal,
30:00they force their way through the cell membrane.
30:10A few days later, they leave in the thousands,
30:14just as these massed cells empty their contents.
30:24Our most important weapons against viruses are the lymphocytes.
30:28They bombard the enemy with antibodies,
30:32small molecules made of protein.
30:38The antibodies are visible as a corona surrounding the cell.
30:47But as effective as these lymphocytes are,
30:50they are no match for the viral disease we call AIDS,
30:54the most feared plague of our time.
31:03This is HIV, the virus that causes AIDS.
31:12HIV uses lymphocytes themselves as host cells
31:16to make copies of itself.
31:21So the cell we count on to kill the enemy
31:25becomes, instead, its victim.
31:29The virus spreads, and we die.
31:42This parasite causes another deadly threat, snail fever.
31:50All it takes is one misstep in a waterhole.
31:56The parasite lives in the stomach of a snail.
32:01It waits patiently for another host animal to pass by.
32:14The parasite larvae then leave for greener pastures,
32:19penetrating the skin of the foot.
32:28Inside the bloodstream, the larvae mature into worms.
32:32Stuck to the walls of arteries and veins, they feed on our blood.
32:38Here you can see the parasite's mouth sucking up blood cells.
32:53The female parasite is thinner than the male
32:56and lives attached to his body.
33:00Their eggs are then carried away by the bloodstream.
33:09They leave our body in urine,
33:12returning to the water and other snails,
33:15completing the cycle.
33:24The parasite is then fed on by the larvae.
33:31Another parasite lives in a mosquito
33:34and causes malaria, a chronic and often fatal disease.
33:43When the mosquito bites,
33:45the parasite is injected through the skin and into the bloodstream.
33:55It lives among our red blood cells,
33:59feeding upon them and reproducing in them.
34:06The blood cells die and the young parasites pour out
34:10to be sucked up by other mosquitoes,
34:14which then bite other victims, spreading the disease further.
34:22Parasites affect animals and humans alike.
34:27They do more damage to both than any other microscopic enemy.
34:39This fight for survival binds all creatures together,
34:43animals, humans, microorganisms.
34:51It's just that some battles are more visible.
34:57The struggle to eat or be eaten is universal,
35:03timeless, inescapable.
35:10But when it comes to the unknown world,
35:13we humans seldom pay attention if we ourselves are not at risk.
35:18And yet all we have to do is take a closer look.
35:30Beneath our very noses we can find a myriad of creatures,
35:34like these scale bugs, who can live their lives in a flower pot,
35:39on a single plant.
35:43Every inch of this greenhouse jungle is inhabited.
35:51And the same kind of drama played out on the African savannah
35:55is found here, even if the protagonists are humbler.
36:02The jungle is a place of peace,
36:05a place where all living things are treated equally.
36:13These aphids are sucking the sap from a leaf.
36:22Here an offspring climbs on the back of one
36:26with its siphon-like tubes.
36:32That's quite handy for these ants,
36:35who treat the aphids like cattle,
36:38herding them from pasture to pasture.
36:44The aphids are then milked of their sap.
36:55But this ladybug wants steak, not milk.
37:00It feasts upon the grazing aphids.
37:04And this red predator mite isn't just hitching a ride.
37:17Another aphid is the target of this hoverfly larva,
37:21which literally eats its prey.
37:24All that's left is an empty shell.
37:55The large butterfly larva on the top is eyed by a landbug.
38:06He's just waiting for the right moment to strike.
38:13Now he's ready and goes in for the kill.
38:25To eat or be eaten,
38:28it's no different from the war within our body,
38:32between viruses, bacteria and our immune system.
38:54In this case, the winner takes all.
39:07Sometimes the battle is between members of the same species.
39:15These two male stag beetles are fighting over a female.
39:24The winner celebrates with the female, waiting for her turn.
39:34From this unique perspective, there is fearsomeness Tyrannosaurus rex.
39:43The combat ends with a lethal cut in the loser's neck shield.
39:48The winner celebrates with the female, waiting beside the battlefield.
39:55They mate, passing on their genes to the next generation.
40:03Evolution rules in the unknown world, too.
40:11The heart of the winner still beats,
40:14the fittest survive,
40:21the sperm of the winner helps shape the future.
40:31Sometimes it's animal versus animal, and sometimes animal versus plant.
40:37These ants have learned to form chains to hold their prey.
40:44They pull together the edges of giant fern leaves.
40:53The result is a nest, food and shelter in one neat package.
41:03The fern is helpless to resist.
41:07This butterfly larva is also free to do as it pleases.
41:15But other plants can give as good as they get, and then some.
41:23Turnabout is fair play in the unknown world.
41:29This ant has picked the wrong plant to eat.
41:37Now he's the meal.
41:41There's no mercy here.
41:53Other plants have developed less deadly defenses against intruders.
41:58This digitalis leaf is really a trap for unwitting insects, foolish enough to land.
42:12Each fiber has a sack of glue at the end,
42:15a sack that bursts on contact, much to the dismay of these aphids.
42:21On the potato plant, the fibers are so long that insects get tangled well above the surface.
42:30This aphid can't reach the leaf to suck up its juice.
42:39This is a plant that's been around for thousands of years.
42:43This aphid can't reach the leaf to suck up its juice.
42:50But other insects, like this plant bug, have come to adapt.
42:57Special claws allow it to walk across the leaf.
43:14All organisms have a part to play in this struggle, whether they know it or not.
43:26A struggle in which life itself will always triumph,
43:31even in the face of death and decay.
43:35It's true in our world and the unknown world.
43:41The more we study them both, the more we see how similar they really are.
43:50The only difference is one of perspective.
44:05If we choose, we can see nature through the eyes of a rhinoceros beetle,
44:10and be grateful we aren't his size.
44:35We can see the garden as an obstacle course.
44:41We can change our entire sense of scale,
44:45and imagine ourselves as the worm instead of the farmer.
44:55We can learn to look beneath our feet,
44:59to see the small, the overlooked, the insignificant,
45:04unusual teachers with different points of view.
45:18We can find a new way of looking at life,
45:22one that's more than just a formality.
45:29We can look more down to earth.
45:44We can even learn more about our own past from the unknown world.
45:53In every pool of water,
45:56there are tiny organisms whose beginnings are linked to ours,
46:01distant relatives to the cells that make up our bodies.
46:10They tell us how life developed and flourished.
46:27Representatives of the first primitive life forms
46:31that led to all the creatures on earth.
46:48The unknown world can also teach us
46:53how our own bodies function.
47:02Like us, the water flea reproduces through live birth,
47:06a microscopic version of our own reproductive system.
47:22Above the eggs of the next generation,
47:25we see her narrow green digestive tract,
47:28and her beating heart.
47:38The processes of life that govern us can be found everywhere,
47:42on the very ground we walk.
47:47Sometimes we're the ant, and sometimes the beetle.
47:51The trick, of course, is to be the predator, not the prey.
47:57The trick is to live another day.
48:03The tunnels of insects can provide a model of our circulatory system.
48:09Arteries in the soil, making possible the flow of nutrients,
48:14An earthworm can help us understand our immune system.
48:22Inside, the same struggle between attacker and defender.
48:29The earthworm can help us understand our immune system.
48:36The earthworm can help us understand our immune system.
48:44On the forest floor, lie clues to our own digestive system.
48:54Here, dead plants and animals are broken down by the living.
49:03In the soil of just one footprint,
49:07there are millions of decomposers hard at work.
49:14Up above, the cycle of life takes another turn.
49:22A new generation must always replace the old.
49:30The dove may not ponder the processes of life and death,
49:34but its fate is the same, nonetheless.
49:44There is only one direction in which to fly,
49:48no matter how extraordinary the journey.
49:56Just as life has sent us on our way, death awaits us all,
50:00the mite, the dove, ourselves.
50:07But the end of the story is also the beginning,
50:11as insects and bacteria turn death into life.
50:15Flies lay eggs that hatch into larvae.
50:23Ants, wasps and beetles arrive on the scene, along with others.
50:35Watch as a process that takes a few weeks,
50:39is compressed into 30 seconds through time-lapse photography.
51:02In 14 days, what was once a beautiful dove
51:07has been broken down by an army of organisms
51:11until only a pile of feathers is left.
51:19And yet everything remains in a different form.
51:27Other animals and plants are using the dove to build new life.
51:37Here, over five weeks, in the same small patch of ground,
51:41spring flowers grow and bloom.
51:45And when they die, there are always others to take their place.
52:16The soil passes on what it has gotten,
52:20only to get it back again in an endless cycle.
52:37A cycle of water and nourishment,
52:42a cycle of day and night,
52:47a cycle of seasons.
52:51Every day, our world and the unknown world meet.
52:55They meet on our teeth.
53:02They meet in our museums.
53:07They meet in our bloodstream.
53:14For better and for worse.
53:23They meet wherever we are.
53:30And so it becomes clear that our world and the unknown world
53:34are really one and the same,
53:38and we are all in it together.
53:42Take a closer look at the technology
53:46that's given us a closer look at ourselves.
53:50From motion studies to fiber optics,
53:54zoom in to NOVA online at pbs.org.
54:12To order this show for $19.95, plus shipping and handling,
54:16call 1-800-255-9424.
54:20And to learn more about how science can solve the mysteries of our world,
54:24ask about our many others.
54:43Tomorrow night on NOVA,
54:47meet the man behind the camera
54:51and discover the secrets at the heart of his greatest work.
54:55Leonard Nielsen revealed on Odyssey of Life Part 3,
54:59The Photographer's Secrets.
55:12NOVA is a production of WGBH Boston.