Bioluminescence & Glow Worms

Added: 2026-05-28

[00:00:00][music] My glowing bug-like eyes at the beginning of the show were not producing any light by themselves. They were simply reflecting light from another source. In this case, they're reflecting light from that torch. And that torch is giving out not only light but also a bit of heat as well. But some lights give out hardly any heat at all. A fluorescent lamp reading lamp such as this one can be on for an hour or more and it hardly heats up at all because it has a special tube inside it that produces light without heat. It's actually producing ultraviolet rays inside that tube. The ultraviolet rays hit the materials inside the glass and those materials glow. It's a little bit like having an ultraviolet lamp such as this one here, which gives out a sort of a purpley glow, but it's also giving out invisible ultraviolet light. And that's the sort of light that gives us a suntan. And if we look at that hitting, say, these two marking pens, you might say, well, there's nothing much at all showing yet. But if we take the studio lights down, you see them glowing because they're giving back to you light of a different kind. And so are the words that have been written with the inks in these pens because they are material called fluorescent materials.

[00:01:31]This is called fluoresence. And that's why of course that reading lamp is called a fluorescent light. It means light is given back to you for a short while because of the ultraviolet light or the other kind of energy that it's absorbed. But there are other kinds of materials that will do this as well.

[00:01:49]Have a look at this material here. Looks like some gooey kind of stuff in a little plastic container. It's actually makeup. So that if I put some of that on my nose and we take the studio lights down again, watch what happens. It actually makes my nose glow because it's fluorescent makeup. Okay? And you can use that for parties or plays or all sorts of things. Put it anywhere you like on yourself and it uh washes off quite easily afterwards. There are other materials though that will continue to glow for a longer period of time. Maybe maybe you've seen these before. Little light sticks they're called. They're actually plastic tubes that contain chemicals which are kept separate because there are little plastic capsules inside there. But if we take the studio lights down, I'll bend the little plastic tube. And by doing so, I bring the two chemicals together and then shake it. And then you see it giving out quite bright greeny yellow light. That's called phosphoresence. And in fact, this little tube will continue giving that light out for four or five hours. And you can make that into a necklace or a bracelet or even a pair of glasses. Quite an interesting little novelty. Well, both phosphoresence, which lasts for a long while, and fluorescent, which lasts for just a short while, are both kinds of luminescence, which simply means giving out light. Believe it or not, there are some animals which are luminescent.

[00:03:14]When you strike a match, you bring together chemicals in the head of the match with chemicals on the side of the matchbox.

[00:03:21]Oxidation occurs and heat and light energy given out. And right now there's another oxidation reaction occurring as the wood burns.

[00:03:31]And when you bring together glycerin, few drops of glycerin, pour it into a heap of potassium permaganate, once again a chemical reaction takes place.

[00:03:43]Oxidation begins to occur and before long, heat energy and light energy are produced. Once again, an example of an oxidation reaction.

[00:04:01]But there's another oxidation process which gives out light energy, and I think it's more fascinating than any of those. It occurs in the body of an animal which is smaller than my little finger, and it lives in New Zealand.

[00:04:13]It's the New Zealand gloworm. And in the Witomo Caves, there are thousands of them. Let's go and meet them.

[00:04:22]I have an individual glowworm here in my hand. It's very tiny. It's only about half the length of my little finger and much much thinner. This is the head end here, the pointy end has quite an appetite. Halfway back along the body is the silk gland and you can see it through the transparent body. And up at the other end is the light organ and it's just starting to glow now, but you won't see that glow properly until we're in the dark.

[00:04:48]The glowworm is actually the laral stage of a flying insect. The total life cycle for this insect is about 11 months. But for nine of those months, it lives as a lava, the glowworm. And the glowworm lives in a little tube at the roof of the cave. The tube is made of mucus and a silk-like material. To catch the prey, the flying insects, what it does is produce a glow in its body, which attracts the insects. And then to catch them, there are threads hanging down, silk-like threads with little sticky drops on them. There can be as many as 50 or 60 of these threads hanging down from one tube and they can hang down for 15, 20, even 30 cm. When the flying insects go into those threads, they're held and the glowworm feels the vibrations just as a fisherman feels the tug on the line when a fish takes the bait and then the glowworm can retrieve the prey. Well, we won't see them until we turn the lights out. Then, if we're lucky, we may see thousands of little lights in the ceiling. Lights off.

[00:05:51]As your eyes become accustomed to the darkness, you gradually become aware of thousands of spots of light in the ceiling of the cave. Each of those tiny glowworms is producing a blue green light in its tail because of a chemical reaction taking place in its body. It's a cold light. Hardly any heat energy is given out. And this is a case of bioluminescence, light produced by a living thing. When a puper hatches into an adult, it only lives for a few days. They're longlegged, two-winged flying insects.

[00:06:21]They look a bit like a big mosquito, but they're hardly ever seen. This one's a preserved specimen. The male and female use the light organs to attract one another. They mate, lay eggs, then die.

[00:06:32]I want to know. [music] Curiosity.

[00:06:43]Curiosity. [music]