Flashing brilliance

DOING the rounds these days is a lovely little book called Under the Durian Tree, a novel by Fergus Linehan

DOING the rounds these days is a lovely little book called Under the Durian Tree, a novel by Fergus Linehan. It tells the story, of an Irish expatriate in the Malayan Civil Service in the closing days of the British Empire. One of his, journeys in that part of the world begins like this:

"I took passage on a small ship that ran along the Borneo coast, past islands that were like jewels in seas that seemed to change colour from dark to blue to shining emerald green. At night the water shone with phosphorescence, and sometimes we could even make out the banks of rivers by the glow of millions of fireflies along them."

Now, here is material to fill up several Weather Eyes - and so it shall. Let us start, not at the beginning, but at the end, by thinking fireflies.

The firefly, as it happens, is not a fly at all, but a member of the beetle family Lampyridae. It is a close cousin of the English glowworm, but a creature, by and large, of the lower latitudes that emits a characteristic flashing light, intended to attract a mate. Some of the larger tropical species flash so brilliantly at night that it is possible to read a newspaper by the light they emit, and in days gone by it was common for a number of them to be kept in a cage to serve as a heatless domestic lamp.

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The firefly's light is produced by organs arranged along the two last segments of beetle's body. The organs contain cells that store a compound known as luciferin, named for obvious reasons after the fallen angel Lucifer, the quondam carrier of light. Surrounding the cells are tubes that can be opened to allow air to enter, and oxygen passing through the tubes reacts with the luciferin to produce the characteristic "cold" light. The ensemble is cleverly provided with reflectors to direct the illumination outwards, the on off sequence of flashes being controlled by the insect's regulation of the oxygen supply.

The firefly's flash is most commonly a shade of green, but some species emit yellow or blue light, and at least one can flash in red. Like light houses, the different species flash with a unique pattern which allows the individual in sect to identify potential partners without embarrassing, or even dangerous, confusion.

As might be expected, the behaviour of the firefly has found its place in folklore. In parts of India, for example, they were believed to have their origins in the sparks escaping from a fire, while in other cultures they were thought to be the eyes of gods that had fallen in fierce battles long ago.