This insect is of little economic importance to us at present but its peculiar habit of producing light makes it a very striking form and one which deserves study. The firefly is a beetle, and begins to make its appearance the latter part of June when the darkest nights may be one solid glow of fire. They live largely in damp places and bottoms at night are specked with their tiny flashes of light. The larval or grub stage is passed on the ground beneath grass, weeds and rubbish where they often prey upon other insects. In some cases the grubs may be able to produce light though as a rule the luminous grub-like creature or glow-worm is a wingless adult firefly.
Observations and Studies
Firefly beetles on sour-dock leaf.
Lower surface of firefly beetle enlarged to show the light producing segments of the abdomen.
Watch for the first appearance of the fireflies in the evening and see where they come from. Do they all appear at once or only a few at first? Do they fly fast? How often is the light produced? Will they produce the light while on the ground? When they fly do they stay near the ground or high in the air? Do they light in trees?
Catch one of the fireflies in your hat and examine it carefully. How large is it? Describe briefly its size, shape and color. Are its wing covers hard like other beetles? Where is the light produced? What color is the light? Is it bright? Hold the firefly on the opposite side of a sheet of paper and see if the light will show through. Try the same with your hat, coat sleeve and other objects. This light is extremely penetrating and unlike the light of a lamp is produced with the generation of very little heat. Will it continue to flash while you hold it? Are the segments from which the light comes the same color as the other segments of the body? Crush the tip of the body between your thumb and finger and see if the light continues to appear. How long does it last? Collect a number of the fireflies and put them in a bottle and see if the light is strong enough to enable you to read.
The firefly has proven to us that our methods of producing light are extremely wasteful since much of the energy is lost in heat and it is possible that through the lesson of the firefly we may some day be able to produce better light at less expense.
