The incandescent light bulb was invented by man towards the end of the nineteenth century — Sir Joseph Wilson Swan patented the design in 1878. Fireflies, on the other hand, have been emitting light since time immemorial, effortlessly, illuminating woods, countryside and our hearts on summer nights, leaving us open-mouthed.

Here are some fascinating facts about these incredible creatures, like tiny shooting stars, which are gradually disappearing due to pesticides and human impact.

1. They are beetles

Everyone knows fireflies, yet not everyone knows that they are in fact a beetle, belonging to the family Lampyridae (Lampyridae). Around two thousand species of firefly have been classified worldwide.

2. Why fireflies light up

The characteristic glow of fireflies, a phenomenon known as bioluminescence, serves the purpose of mating — the light allows males and females to see one another. The female can emit light for over two hours, whereas the male does so only for brief moments.

3. Fireflies are alchemists

Alchemists spent centuries trying to uncover the secrets of the transmutation of substances and metals. Fireflies hold that secret within themselves. These insects cannot transform iron into gold, but they can generate light. Fireflies absorb oxygen and, inside specialised cells, combine it with a substance called luciferin; this triggers a chemical reaction capable of producing light with almost no heat.

4. The light emitted by fireflies is the most efficient

The light produced by fireflies is perhaps the most efficient that exists. An incandescent lamp, for example, converts around 10 per cent of its energy into light, with the remaining 90 per cent dispersed as heat. A firefly, by contrast, is able to use almost 100 per cent of the energy generated by the chemical reaction to produce light.

5. Firefly numbers are declining

Firefly populations, effective indicators of environmental health, are in decline in several parts of the world, particularly in Italy. The gradual disappearance of these creatures was described by Rachel Carson in her bestseller "Silent Spring" and by Pier Paolo Pasolini in a famous article from 1975. The main causes of the fireflies' disappearance are the use of pesticides, urbanisation and light pollution. Pesticides kill the larvae that could otherwise be excellent allies for farmers, as they feed on slugs, snails and other insects harmful to crops.