Attracting Fireflies: Making New Backyard Friends

Mild winters trigger larger firefly populations. Once summer-like weather appears, usually mid-May to the third week of June, adult fireflies begin their brilliant light shows in gardens and backyards across North America. If the weather in late spring is super-warm and inviting, it lures these fantastical critters into an early arrival. As the nights cool off, the time between the light flashes increases. Once fall arrives, the light from the fireflies fades away.

Fireflies love peaceful, warm, humid, and dark surroundings. Their neon auras are brighter and their flashes are more prominent on balmy nights. A rain-filled spring season with higher humidity levels will also encourage larger colonies.

Firefly larvae love to munch on the bugs that emerge from the damp soil following a good rain. Droughts, however, are a major stressor for firefly populations. Heat stress kills larvae before they ever emerge from the soil.

Long grasses, such as deer grass or inland sea oats, and shrubberies like dogwood, help provide cover for adult fireflies during the day and retain the soil’s moisture and humidity levels. Firefly moms need a proper nursery to hatch their eggs, preferably an area with lots of greenery and accumulated log and leaf clutter. During the day, adults hide out in tall grass or under leafy plants. At night, females usually crawl to the top of the blades of grass or onto tree branches, while males tend to fly around in search of the perfect glow from a potential mate. During the day, trees provide much-needed shade. Pine trees, pecan trees, sycamores, and cottonwoods are some of the firefly’s favorites.

Fireflies can usually be found near ponds, lakes, rivers, streams, and marshes. Seasonal pools of water — vernal pools — are prime habitats for the array of insects that firefly larvae love to snack on. Any area with even small depressions of standing water is a top choice during the yearly two-week mating season. A small pond surrounded by greenery creates a perfect spot for firefly courtships. However, if your area has a mosquito problem, a standing water feature may not be a great choice.

Some adult fireflies don’t eat at all, but most feed primarily on dewdrops, flower nectar, and pollen. Others feed on smaller insects. Planting asters, goldenrod, frostweed, morning glories, and purple leather flower and dewberry vines will not only attract fireflies but also provide the nourishment the adults need. Fireflies spend about 95% of their existence in the larval stage, living up to two years in the soil, mud, or under leaf cover. Larvae eat slugs, snails, worms, and sometimes, adult fireflies.

Fireflies are nocturnal and wait until it’s dark before beginning their striking display. The insects communicate with each other by flashing their lights. Bright security and ornamental garden illumination may interfere with your goal of attracting fireflies. Scientists believe that artificial lights disrupt the flashing or blinking communications fireflies use for finding mates, which could lead to fewer fireflies being born. It’s best to turn off those exterior lights.

In addition to bright lights, drought, and overly warm temperatures, other situations can deter fireflies, lead to their early demise, or inhibit their reproduction cycles.

• Don’t use broad-spectrum pesticides and fertilizers, such as lawn chemicals.
• Don’t over-mow the lawn.
• Avoid walking through the habitat.
• Don’t let the soil in the habitat dry out. Water when necessary.

Although fireflies may discover a new habitat within a year, it can take up to five years for them to find yours. Fireflies may abandon habitats where there is construction or other encroachments. They may also move to a smaller habitat nearby if the one they are living in becomes too crowded, even if the smaller one is less beneficial. Creating a safe environment with plenty of food to eat and lots of plant cover is more likely to attract a healthy colony.

A firefly’s signature glow is a type of natural illumination known as bioluminescence that comes from photic organs in the lower end of the firefly’s abdomen. The light they emit is a cold light, meaning the energy used to create the bright glimmer produces no heat.

The reaction between three different chemicals is responsible for luminescence. The chemical ATP exists in all living things, but in fireflies, it initiates this luminosity. Luciferase, an enzyme, triggers the emission of light. The heat-resistant chemical luciferin glistens under specific light conditions. In some species, the larvae and eggs emit light, too.

Researchers believe that the loss of habitats, in combination with urban sprawl, light pollution, and the wide use of pesticides, may have diminished firefly populations. Organizations like Firefly Watch have asked the public to submit their observations about firefly sightings, colony numbers, flash patterns, and the habitats where participants observe them. Researchers hope that the program will hone in on the geographic locations of firefly species and the and environmental impacts on them.