Thursday, May 06, 2010

Firefly’s life cycle and habitat

There have always been fireflies in our gardens. Some years there have been a few less, some years many more fireflies than usual. The reason for these swings in population not being clear, I decided to find out what sort of habitat would ensure abundant firefly reproduction.

Fireflies, or lighting bugs as some call them, are actually beetles. There are a couple of thousand species around the world with several living and breeding here in North America. The amount of light at night especially in urban areas, moisture in the soil, decaying organic matter, and available food sources determine which species you will be seeing.

Adult female fireflies lay their eggs in moist soil or moss (depending on species). A few weeks later the larvae emerge. They live in moist soil or beneath decaying organic litter from one to three years eating slugs, worms and soft bodied insect larvae. Firefly larvae sometimes work together on larger prey such as the slugs, first biting the creature releasing saliva that turns the prey’s soft inner tissue into liquid. Firefly larvae can actually track slime trails to find slugs and snails. In late spring larvae pupate underground assuming their adult form. When the weather warms or to circadian like cycles not yet understood, the adult emerges to mate. This is the part of the life cycle of fireflies many recognize. As dusk descends and evening light wanes flickering lights appear over lawns, open meadows and along waterways across eastern North America. The fireflies are signaling their desire to mate.

So what makes for a firefly habitat in the garden? Seems wet springs producing moist soils and lots of decaying organic matter where slugs and worms and other larvae live, along with dark corners of a garden where trees and shrubs shade open areas from street and home lights.

There appear to be several reasons why firefly populations tend to decline in any given area. Average temperature and rain fall amounts ,pesticide usage, artificial lighting along streets and the outside of homes, amount of organic litter and loss of habitat including the expanses of lawn where female firefly can not lay eggs, all influence firefly survival. There is also some evidence that firefly populations do not move away from where they started life so that local populations once lost completely do not recover on their own.

A backyard habitat can make a difference.

For more information check out the following sites. Fieldguide

Life Cycle: Winter is spent in the larval stage in chambers formed in the soil.
They pupate in the spring and emerge in early summer.
After mating females lay spherical eggs singly or in groups in damp soil.
Larvae hatch from eggs in about 4 weeks and larvae develop through several stages (instars) before pupating.
The life cycle of most species takes two years.

Habitat and Food Source(s):
Mouthparts are for chewing. Immature stages of lightning beetles are predatory on other small insects, earthworms, slugs and snails. Adults of some species are also predatory. Larvae and adults are active at night (they are nocturnal), and immobilize their prey by injecting them with inject toxic digestive enzymes before sucking out the liquefied body contents. fireflies blog, where have all the fireflies gone?

Picture of firefly image firefly larva

Sara Adler "Summer flings: firefly courtship, sex, and death". Natural History. 06 May, 2010.

Bounty hunters, too, may have been contributing to declining firefly populations. For about forty years the Sigma-Aldrich Corporation in St. Louis, seeking luciferin and luciferase, sponsored a firefly-collecting club. The company paid a network of collectors nationwide a penny a firefly (with quantity bonuses that total $600 for 200,000 fireflies). Millions were collected. Although a few firefly species might be abundant enough to support such harvesting, many less-abundant species (and species are collected indiscriminately) could readily be snuffed out. Fortunately, there is no longer any reason to collect fireflies from the wild. Synthetic luciferin has long been available, and the firefly luciferase gene has been cloned. Sigma-Aldrich ended the collecting club a few years ago.