Last summer, halfway through a trip across South India, I spent the night in a tiger reserve. It was unusual for me – I like nature, but only if it’s easy to find, easy to understand and unlikely to do me any harm. A museum would probably have been a better choice.

There’s not a lot to do in a nature reserve after sundown, so we ended up chatting to one of the few other guests, a middle-aged man from Tamil Nadu who was very excited at the chance of spotting a tiger during his stay. Earlier in the day he’d warned us against leaving the hotel porch at night, just in case; but by evening, he seemed to have forgotten his own advice. As my friend and I sat reading and swatting away insects, he roamed the grounds with a torch in search of creatures.

“Surely he won’t find anything?” I whispered. Being city-born and British, on some level I refuse to believe that the countryside can yield anything interesting at all, tiger reserve or no. But the odds really weren’t good. Mudumalai alone contains over 300 square kilometres of forest, and it sits within the 5520km² Nilgiri Biosphere Reserve. At last count, there were 48 tigers.

“It takes luck and determination,” the park’s website informed us before we came, “to spot one of these big cats that are such masters of secrecy.”

Although he wasn’t lacking in determination, our friend was short on luck. It was some time later that he reappeared on the porch, cupping something significantly smaller than a tiger in his palm.

“Minminni, in Tamil,” he informed us, shaking a centimetre-long firefly into my friend’s hand before cheerfully wandering off again.

Fireflies had been flaring around us all evening, but this was the first time I’d seen one up close. The V-shaped luminous strip on its back was surprisingly green and artificial-looking, as if someone had stuck on an LED.

When a living organism produces light, we call it bioluminescence. Quite a few species have this ability, although the firefly is one of the few land-dwellers to be able to do it. It happens because fireflies can produce a type of chemical known as a luciferin. Like the fallen angel, the morning star and the brand of matches, luciferin gets its name from the Latin for ‘light-bearing’. And that’s just what it does – it goes through a chemical reaction that lights the firefly up.

If luciferin is available, and so are oxygen, calcium and adenosine triphosphate (or ATP – this is the chemical that powers living cells, so it’s readily available in most alive things) then it can enter a reaction with an enzyme called luciferase. Like many chemical reactions, this releases energy – in this case, the energy takes the form of a very bright light.

A lot of bioluminescent animals light up to attract food – think of the anglerfish – but this isn’t the case with fireflies. As far as we know, it’s purely a mating display – females judge males on the quality of their flashing (sorry.)

Different types of firefly also flash in different patterns, a clever trick that’s evolved to let fireflies of the same species identify each other in a crowd of unsuitable mates. Unfortunately, some fireflies have evolved an even cleverer trick to exploit it. Fireflies from the Photurus genus are capable of mimicking the flash pattern of their close relatives, Photinus fireflies. They do this to lure in Photinus males and eat them.

It seems Photinus fireflies have developed a predator-repellent chemical in their blood – essentially, whenever a predator comes by they just bleed a bit and the predator backs off – which Photorus fireflies lack. By feeding on a Photinus, a Photurus gets to take all the protective gunk for herself.

Thanks to all the evolutionary hard work put in by fireflies and their ilk, modern scientists can use luciferins to light up any organism that takes their fancy. Usually this is because it’s handy for tracking the take up and expression of other, more conventionally useful genes that have been added during genetic modification. At other times, it’s just for fun.

Earier this year, a Kickstarter project  raised $480,000 to fund the development of bioluminescent plants. The scientists involve call themselves ‘bio-hackers’ – citizen scientists (admittedly, mainly PhDs with day jobs in labs) expressing their enthusiasm for nature’s delicate engineering by taking it apart, tinkering with it and putting it back together, better.

Glowing plants are nothing new, but the team is ambitious. They see the commercial potential behind a glowing rose, and (in theory, at least) have their eye on a bigger, environmental goal: city streets lined with luminous trees, a semi-natural substitute for streetlights.

It’s a long way to come from a little strip of light on a bug in a dark forest. That firefly was about it as far as nature went, that night – I didn’t encounter anything with fewer than six legs. Our friend told us he’d caught the glitter of some deers’ eyes in his torch beam, but they were gone before I got a look. “Maybe they saw some tigers,” he ventured.

When we went to bed he was still sitting up on the porch, wrapped in a blanket and intently watching the forest as fireflies continued to flash bright in the darkness in front of him. He assured us he’d knock on our door if any tigers came by. We wished him goodnight and, privately, I hoped he’d get a sighting of what he was looking for.