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Firefly Watch

One of my anticipated events in June is the nightly, blinking light show of the fireflies. This year did not seem as spectacular as other years and it lead me to wonder. Considering that I know next to nothing about these wonderful beetles, it gave me cause to write this article.

So had the wet and cold spring adversely affected the firefly? It turns out to be a more complicated issue than just adverse weather conditions. As far back as 2010, scientists from around the world knew our beloved firefly was in trouble. During the International Firefly Symposium, 13 nations documented noticeable population declines and declared an urgent need for conservation of their habitats. Just conserving habitat is not enough.

In order for the following conservation steps to make sense we need to understand the firefly. Did you know that there are thousands of firefly species and that they are found on every continent of the world, except for Antarctica? Some species are almost aquatic and have gills while other species live entirely in trees. What is common to all of them is their need for a moist environment to survive. In North America, we have the class of Photini firefly and the most common one we see in our backyards is the Eastern Firefly.

Firefly attracting mate

Overall, their lifespans are short. Eggs develop in 3 weeks, followed by a 1 to 2 year, in ground, larva stage followed by 3weeks pupating and, finally, emerging as the adult firefly beetle. Adults are short lived, only 3 to 4 weeks. The mating courtship is beautiful to watch at night – but first we must understand how fireflies blink.

Fireflies produce ‘cold light’. This is how they communicate to one another and other insects. In a firefly’s tail there are 2 chemicals : luciferase and luciferin. Luciferin is heat resistant and glows only under the right conditions. ATP, a chemical found within the firefly body, combines with luciferase (an enzyme) to initiate the cold light. Fireflies emit this cold light mostly to attract mates but the light can also be used to defend territory and warn predators away. In some fireflies, only one sex can initiate cold light. However, in most species, both sexes have the ability to produce light where the male will fly blinking and waiting for a response from a female. Females will wait in trees, shrubs and long grasses and signal an attractive male. Every specie of firefly has its own unique and distinctive pattern of color, frequency and sequencing of flashing.

The female firefly throws a twist into the mating game. The male, when signaled by a receptive female, will seek her out and try to reproduce. The female either, eats or reproduces with the male. Why eat a potential mate? Only males have chemicals in their blood, called lucibufagins, that are bitter and can be poisonous. So very similar to the Monarch butterfly, predators learn not to eat them for fear of being sickened or poisoned. When attacked, the male firefly will ‘reflex bleed’ whereby shedding drops of blood with lucibufagins. Unfortunately, the female firefly does not have the ability to produce lucibufagins and must acquire the blood chemical by ingesting the male firefly. They protect their eggs by passing the acquired poison along.

So how can we help this amazing beetle? Here are some recommendations you can implement in your own backyard.


Fireflies communicate through their flashing lights and especially to attract mates. Human light pollution disrupts their flashes making it harder to find mates and breed. Even drawing blinds at night for inside lights will help dim your surrounding outside yard.


Have logs and leaf litter handy. Some species of fireflies grow in rotten logs and leaf litter. Create water features. Most species of fireflies thrive around standing water and marshy areas. Ponds, streams and rivers can also provide good habitat. Even a small ground depression full of water can cause them to congregate. Fireflies eat the smaller insects, grubs and snail that live near these water landscapes.


Fireflies and their larva may come into contact with other pests that have been poisoned, or they may ingest poisons from plants that have been sprayed. Remember – firefly larva eat other undesirable insects, so they are nature’s natural pest control.



Fireflies mainly stay on the ground during the day, and frequently mowing may disturb populations. Consider incorporating some areas of long grasses in your landscape. Fireflies prefer to live in long grasses.

Some very simple changes to your gardening and landscape can be of great importance to this beetle. I’m hoping we will all try these recommendations so that we can continue to witness the amazing firefly display on a summer’s night.

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