The lightning bug has been flashing up the night skies

Al Lowe
Contributor

Look up at night and you can see an interesting little phenomenon of the insect world. The fireflies are courting. Some animals do their courting with gifts, some with song, and some with various displays of colour or acrobatics. The fireflies do it with light.
As you drive along the country roads at this time of year, you can see the tiny flickering lights over the fields, by the hundreds of thousands. If you watch carefully, you will see that the little flashes of light do not occur completely at random. They are quite regular - a fixed number of seconds apart. However, all species do not flash at the same rate, and quite often the males emit a brilliant flash, while the females emit a dimmer, more demure one. The display over a hayfield can be quite a sight on an early summer evening.
There are about 2000 species of true fireflies, family Lampyrida. These are all beetles, some of them quite small, a quarter to a half inch in length. They are flattened down, and in the daytime, they are quite inconspicuous, in browns, greens and reddish brown. These little beetles have their light organs on the back segments of their abdomens. The light producing action is quite complicated, but it involves a substance called ‘luciferin’ reacting with an enzyme called ‘luciferase’. This action is controlled by the insects nervous system. There is also a reflecting layer of cells which makes the light production more efficient.
The light produced is always part of a continuos spectrum, with no lines, either bright or dark. The fireflies, light is about 95% efficient compared to about 5% for an ordinary household light bulb. Some fireflies produce bright yellow light, some greenish or blue, but a lot of them get along with just plain old white.
We do not have many species of fireflies in northern Ontario, but there are many, many insects around the world which produce light. In some species, the larvae (the grubs) produce the light. These are the true ‘glow-worms’.
The most remarkable glow-worm is in South America. The female of this particular species produces green light from its abdomen, and bright red lights from its head. It can turn on these light both at once or one at a time. In Asia, there are luminous insects which can flash together. A whole cloud will gather in a tree, and then the whole tree will switch on and off at the same time.
This form of light production has been under study for a very long time. To be able to produce light efficiently, and without heat, is a very attractive proposition. The applications for travel, space, and plain everyday living would be enormous.
So take a look at the humble little fireflies at dusk some evening. Like many other creatures in the natural world, these little insects have chemical secrets which we have not yet been able to master.