We’re not quite ready to welcome lightning bugs

Every year, young and old alike await the annual occurrence of fireflies.

Fireflies, also known as lightning bugs are an insect in the beetle family Lampyridae, are a summertime favorite. Even the most squeamish among us must admit awe and fascination over these beetles with the glowing bottoms.

So where are the lightning bugs this year?

Cooler spring weather likely slowed things down a bit. Like all beetles, they undergo complete metamorphosis. Their lifecycle involves an egg, larva, pupa and adult eggs are laid in moist humus, leaf litter or moist soil.

Upon hatching, many Ohio species will spend two or more years as predatory larva in the soil eating snails, slugs, worms, and other smaller soil arthropods like springtails! They then pupate and appear as adults to feed, mate and lay eggs. Waiting for those adults to appear is what we’re doing now.

Like Bagworms, we use growing degree days or Phenology to predict adult emergence. Phenology is the development of both plants and insects and is temperature dependent. Plants can accurately track the environmental factors that decide when insects are active. For this reason, plant phenology can be used to predict insect emergence. To track these activities, we look at Growing Degree Days.

Adult fireflies begin to appear when we reach 950 growing degree days and are at their peak at around 1,094 growing degree days. On June 20, Wood County was at 887 growing degree days. We are getting closer but are not quite there yet.

An indicator plant that flowers the same time that lightning bugs begin appearing is the Little Leaf Linden (Tilia spp.).

Many firefly species are aquatic or semi-aquatic, favoring moist habitat along streams, transition zones between forests and fields, taller grass and humid areas. With the relative absence of rainfall, the past several weeks this may lead to an overall decline of firefly activity.

Other factors that may decrease their presence is insects often go through cycles of booms and busts. Population cycles of insects can be affected by winter temperatures, moisture, humidity, predator populations, diseases, and more. This occurs naturally through predator-prey relationships, available food, and weather. Besides these natural threats, there are external threats to fireflies as well. We cannot ignore that human impacts have caused a decline in lightning bugs’ overall populations.

Habitat degradation and loss from humans is a major concern for fireflies and other insects. These factors include light pollution, use of pesticides and climate change.

How can we help? In your own landscape, use leaf mulch or wood mulch around plants to mimic the humus layer where eggs may be deposited, and to conserve moisture. Preserve waterways and aquatic habitats that lightning bugs will favor. Reducing outdoor lighting also helps them to show off their lights and find each other to mate and produce the next successful generation of our favorite summertime light show.

Be on the lookout for fireflies, and do what you can to help keep them a summertime favorite for generations to come.