Thanks to some elementary students in Upper Darby, the firefly was officially named the state insect of Pennsylvania in 1974. Many of us have fond childhood memories of chasing and capturing these “lightning bugs” in jars. However, a decline in the population threatens to rob future generations of children of being able to experience these same memories.
“The global decline is roughly 1-2% per year or 10-20% per decade. Approximately 13% of all firefly species are either threatened or endangered,” says Dr. John Wallace, professor of entomology and co-coordinator of the MU Watershed Education Training Institute.
Fireflies are not actually flies and they do not create fire. In fact, they are actually beetles that possess luciferase, an enzyme that, through an internal chemical reaction, allows them to produce light. Luciferin, the molecule that luciferase acts upon, is used in LED lights. It is also in medical technology for detecting blood clots, understanding Parkinson’s disease, visualizing HIV and developing cancer treatments.
The biggest threats to firefly populations are loss of habitat, overuse of pesticides, invasive species such as fire ants impacting larvae by preying on them, water quality declines in and around their habitats, overcollection by people and climate change. Increases in light pollution make it more difficult for some species to reproduce as some require complete darkness to find mates. Adult fireflies only live for about a month, but the larvae may take up to two years to develop into an adult firefly, so protecting the larvae is the key.
“The name of the game in nature is to live to reproduce – larvae do not reproduce so protecting larval habitats is essential to maintaining populations. With increased wetland destruction, it is not a stretch to see how their populations are in decline,” says Wallace.
Firefly larvae live in wet habitats such as along streams, in wetlands and in damp fields. The adults live in and around these places so that they can lay eggs in the areas where the larvae will have food.
So, what can people to help stop the decline of the firefly population? According to the Xerces Society, there are many things we can do, such as:
- Leave areas of leaf litter on your land or lawn.
- Mow less, or better yet, replace your lawns with native plants.
- Use fences to keep cattle out of fragile wetlands.
- Reduce ground-disturbing activities or do them on a rotational basis.
- Reduce or eliminate the use of chemical fertilizers and pesticides (especially broad-spectrum pesticides like neonicotinoids).
- Allow slugs and snails to live. Firefly larvae love to eat them!
- Eliminate invasive species.
- Reduce unnecessary outdoor lighting and close your blinds at night.
- Participate in community science projects likeFirefly Watch
“Fireflies are predators feeding on snails and slugs – which are pests in our gardens and yards. So, they serve as biocontrol agents for pests and allow us to reduce pesticide use by naturally feeding on these pests,” says Wallace.