HOW TO HELP

Fireflies are disappearing all over the world, and it’s believed to be
because of human encroachment on habitat and increased light pollution
from development and traffic. But there are a few things you can do to
help fireflies make a comeback in your area.

None of these steps have been proven to work, mainly because scientists
have only been studying firefly populations for a few years and data is
still inconclusive. But signs point to human development, light pollution
and toxic chemicals as likely culprits behind the dwindling of firefly
populations. Follow these steps, and with luck your yard will once again
sparkle on summer nights.

Turn off outside lights at night.

Fireflies use their flashing lights to signal each other, attract mates
and warn of danger. While the science is still preliminary, it’s likely
that human light pollution can disrupt their flashes—making it harder
for fireflies to find mates and breed. This leads to fewer fireflies mating
and smaller numbers in subsequent generations. You can make your yard
a haven for fireflies by turning off exterior and garden lights, and drawing
your blinds at night so that interior light doesn’t brighten your yard
too much.

Let logs and litter accumulate.

Some species of firefly larvae grow up in rotten logs and the litter
that accumulates beneath the forest canopy. To encourage their growth,
plant some trees on your property. If you have trees in your yard, consider
leaving some natural litter around them to give firefly larvae a place
to grow.

Create water features in your landscape.

Most species of fireflies have one thing in common: they thrive around
standing water and marshy areas. Ponds, streams and rivers can all provide
good habitats for fireflies, but even a small depression full of water
can cause them to congregate. Build a small pond or divert a small stream
to run through your property, and it’s more likely you’ll see fireflies
at night. Chemically treated swimming pools aren’t a good substitute;
fireflies are believed to eat the smaller insects, grubs and snails that
thrive in natural ponds and streams, and these don’t live in chlorinated
environments.

Avoid use of pesticides, especially lawn chemicals.

It’s likely that chemical pesticides and weed killers may also have a
negative effect on firefly populations. Fireflies and their larvae may
come into contact with other insects that have been poisoned, or they
may ingest the poisons from plants that have been sprayed. Avoid using
pesticides on your lawn and you may boost firefly populations.

While no formal studies have been done specifically targeted to the effects of lawn chemicals on fireflies. Two known studies indirectly suggest that these chemicals may be harmful to fireflies and larvae. The first study suggests that lawn chemicals are toxic to insects in the lawn where firefly larvae are found [1]. The other study provides proof that lawn chemicals are very toxic to the food that sustains firefly larvae [2]. Both show that lawn chemicals can have a serious detrimental effect on fireflies throughout all growth stages.

The best thing you can do to support fireflies is stop using lawn chemicals and broad spectrum pesticides. Firefly larvae eat other undesirable insects, so they are nature’s natural pest control.

A notable example of how pesticide overspraying has affected a local population
is the extinction of the dusky seaside sparrow who was native to the salt
marshes of Merritt Island in Florida. Its habitat was sprayed with DDT
to control mosquitoes and human development quickly changed the ecosystem
so much that the bird could not compensate and went extinct.

Many communities over spray for mosquitoes at night just when fireflies
are active, flashing and mating. Such over spraying can wipe out firefly
populations. These same communities often do not implement more effective
control of mosquitoes, such as neighborhood programs to reduce standing
water, especially in swimming pools, and usage of mosquito larvacides
to prevent the growth and development of mosquitoes in drainage ditches.
By encouraging broad spectrum mosquito control efforts and discouraging
spraying at times when fireflies are active, communities can actually
save money and effect better control of mosquitoes, causing less impact
to firefly species and other small animals.

Use natural fertilizers.

While no conclusive studies have been done, it’s possible that chemical
fertilizers may have a harmful effect on firefly populations as well—especially
since many harmful chemicals in pesticides are also found in chemical
fertilizers. Using natural fertilizers may make your yard a more healthy
place for fireflies.

Don’t over-mow your lawn.

Fireflies mainly stay on the ground during the day, and frequent mowing
may disturb local firefly populations. While you may feel that you need
to keep your lawn mowed for aesthetic purposes, consider incorporating
some areas of long grasses into your landscaping. Fireflies prefer to
live in long grasses, and doing this may boost their population in your
yard.

Plant native trees.

Fast growing pine and native trees provide a good habitat for many species
of fireflies. Naturalist Terry Lynch, who has studied fireflies for many
years, recommends Pine trees because they provide shade and the low light
area provided by a canopy actually increasing the amount of time fireflies
have to find a mate. Also, the litter produced by pine trees, if left
to accumulate, provides a good habitat for earthworms and other small
animals which firefly larvae feed upon.

Do NOT introduce earthworms to you yard.

What’s so bad about a worm? For many of us, seeing earthworms under rocks,
on sidewalks after rainstorms, and in our gardens is just a fact of life.
Few of us think to question the presence of worms or their impact on fireflies.

The truth about earthworms is this: they are not native to any of the northern
United States or Canada. Any worms that were here originally were wiped out during
the last glaciation. It would be pretty hard for a creature that lives in the
upper topsoil to survive the crushing weight, scraping, and sedimentary deposits of
a mile-thick hunk of ice.

The impact of earthworms is not limited to plants. The reduction in plant diversity
and leaf litter affects the habitat and food availability of insects such as fireflies, which affects the
food chain on up, reducing the food available to reptiles, amphibians, birds and small
mammals.

The earthworms we currently have in the region are of European origin (which are
the same species that you can pick up at a bait shop) and were introduced by settlers
~300 years ago and have been on a human aided journey west since then. These non-native
earthworms are contributing to some ecological effects in these glaciated areas
that for the last ~12,000 years developed earthworms free. There are native earthworms
along the East coast of North America but these populations are small and localized.
Current research in that area is showing that these non-native earthworms are having
negative effects on native earthworm species also.

Talk to your neighbors.

If you live in a suburban area in close proximity to others, what you
do in your own yard will help—but you can create even more habitat for
fireflies by enlisting your neighbors in your efforts. Tell your neighbors
about your concern over dwindling firefly populations and what they can
do to help. If you convince even one or two people on your street, you
could help increase firefly habitat in your area even more.

Fireflies are disappearing all over the world. But there are a few things
you could do to help—and every little bit counts. Allow some room for
wildness on your property—low-hanging trees, forest litter, and long grasses
all create welcoming environments for fireflies. Ponds and streams are
crucial to firefly populations, and you can further encourage their numbers
by reducing the amount of light in your yard at night and by cutting back
on chemical fertilizers and pesticides. Follow these tips, and it’s possible
you could see a resurgence of fireflies in your area.

References:

1. "Understanding Halofenozide (Mach 2) and Imidacloprid (Merit) Soil Insecticides," by Daniel A Potter. International SportsTurf Institute, Inc., Turfax, Vol. 6 No. 1 (Jan-Feb 1998)

2. "Relative Toxicities of Chemicals to the Earthworm Eisenia foetida," by Brian L.
Roberts and H. Wyman Dorough. Article first published online: 20 Oct 2009.
Environmental Toxicology and Chemistry, Vol. 3, No. 1 (Jan. 1984), pp.
67–78.