In some species there seems to be a most romantic reason for their brilliance. Down among the grass blades are lowly, wingless creatures--the female fireflies, which, as twilight falls, leave their earthen burrows in the turf and, crawling slowly to the summit of some plant, they display the tiny lanterns which Nature has kindled within their bodies.
Far overhead shoot the strong-winged males, searching for their minute insect food, weaving glowing lines over all the shadowy landscape, and apparently heedless of all beneath them. Yet when the dim little beacon, hung out with the hopefulness of instinct upon the grass blade, is seen, all else is forgotten and the beetle descends to pay court to the poor, worm-like creature, so unlike him in appearance, but whose little illumination is her badge of nobility. The gallant suitor is as devoted as if the object of his affection were clad in all the gay colours of a butterfly; and he is fortunate if, when he has reached the signal among the grasses, he does not find a half-dozen firefly rivals before him.
When insects seek their mates by day, their characteristic colours or forms may be confused with surrounding objects; or those which by night are able in that marvellous way to follow the faintest scent up wind may have difficulties when cross currents of air are encountered; but the female firefly, waiting patiently upon her lowly leaf, has unequalled opportunity for winning her mate, for there is nothing to compare with or eclipse her flame. Except--I wonder if ever a firefly has hastened downward toward the strange glow which we sometimes see in the heart of decayed wood,--mistaking a patch of fox-fire for the love-light of which he was in search!
In other species, including the common one about our homes, the lady lightning-bug is more fortunate in possessing wings and is able to fly abroad like her mate.
Although this phosphorescence has been microscopically examined, it is but slightly understood. We know, however, that it is a wonderful process of combustion,--by which a bright light is produced without heat, smoke, or indeed fuel, except that provided by the life processes in the tiny body of the insect.
So shines a good deed in a naughty world. Shakespeare.