Life Cycle of Fireflies and Lightning Bugs

The 4 Stages of a FIrefly's Life

Firefly larva.
Firefly larvae look quite different from the familiar adults. Getty Images/Hans Lang

Fireflies, otherwise known as lightning bugs, belong to the family Lampyridae in the order Coleoptera, the beetles. Like all beetles, fireflies undergo complete metamorphosis with four stages in their life cycle: egg, larva, pupa, and adult.

Globally, there are about 2,000 species of fireflies, with over 150 species in the U.S. and Canada. This is a general description of the firefly life cycle.

Egg – Embryonic Stage:

The firefly life cycle begins with an egg.

In mid-summer, mated females will deposit about 100 spherical eggs, singly or in clusters, in the soil or near the soil surface. Fireflies prefer moist soils, and will often choose to place their eggs under mulch or leaf litter, where the soil is less likely to dry out. Some fireflies will deposit eggs on vegetation rather than directly in the soil. Firefly eggs usually hatch in 3-4 weeks.

The eggs of some lightning bugs are bioluminescent, and you may see them glowing dimly if you're lucky enough to find them in the soil.

Larva - Larval Stage:

As with many beetles, lightning bug larvae look somewhat worm-like. The dorsal segments are flattened and extend to the back and sides, like overlapping plates. Firefly larvae produce light, and are sometimes called glowworms.

Firefly larvae usually live in the soil. At night, they hunt slugs, snails, worms, and other insects. When it captures prey, the larva will inject its unfortunate victim with digestive enzymes to immobilize it and liquefy its remains.

Larvae emerge from their eggs in late summer, and live through the winter before pupating in the spring. In some species, the larval stage lasts well over a year, with the larvae living through two winters before pupating. As it grows, the larva will repeatedly molt to shed its exoskeleton, replacing it with a larger cuticle each time.

Just before pupating, the firefly larva measures about ¾" in length.

Pupa – Pupal Stage:

When the larva is ready to pupate, usually in late spring, it constructs a mud chamber in the soil and settles inside it. In some species, the larva attaches itself to a tree's bark, hanging upside down by the hind end, and pupates while suspended (similar to a caterpillar).

Regardless of which position the larva assumes for pupation, a remarkable transformation takes place during the pupal stage. In a process called histolysis, the larva's body is broken down, and special groups of transformative cells are activated. These cell groups, called histoblasts, trigger biochemical processes that transform the insect from a larva into its adult form. When the metamorphosis is complete, the adult firefly is ready to emerge, usually about 10 days to several weeks after pupation.

Adult – Imaginal Stage:

When the adult firefly finally emerges, it has only one real purpose – to reproduce. A firefly's focus is on finding a mate, a task made easier by its ability to signal other fireflies with its light. Though not all species of fireflies produce light, those that do flash a species-specific pattern to locate compatible individuals of the opposite sex.

Typically, the male flies low to the ground, flashing a signal with the light organ on his abdomen, and a female resting on vegetation returns his communiqué. By repeating this exchange, the male homes in on her, and the rest of the story is happily ever after.

Not all fireflies feed as adults – some simply mate, produce offspring, and die. But when adults do feed, they are usually predaceous, and hunt other insects. Female fireflies sometimes use a bit of trickery to lure males of other species closer, and then eat them. Not much is known about firefly eating habits, however, and it is thought that some fireflies may feed on pollen or nectar.

In some species, the female adult firefly is flightless. She may resemble a firefly larva, but have large, compound eyes. Some fireflies don't produce light.

For example, in the U.S., where we find beetles in the family Lampyridae from coast to coast, those species found west of Kansas don't glow.

 

Sources:

  • Enjoy the Light of the Firefly, Iowa State Extension Service, accessed October 9, 2012
  • Firefly, Texas A&M Extension Service, accessed October 9, 2012
  • Everything is Illuminated: A Teacher's Guide to Fireflies, Cornell University Extension Service, accessed October 9, 2012
  • Firefly, HYG-2125-95, Ohio State University Extension Service, accessed October 9, 2012
  • Museum of Science Firefly Watch | Understanding Fireflies, accessed October 9, 2012