My friend, the blogger over at the Musings, Mischief and Mayhem asked a question about fireflies. She wants to know why are there a lot of fireflies in northern Alabama right now (first part of August), but she isn’t seeing any in Tallahassee, Florida. Is it because it is a wet year? Is it because the city is spraying for mosquitoes?
Because I know that there are a lot of different species of fireflies (also known as lightning bugs), I first checked to see when adult fireflies have been sighted in the past in Tallahassee. A quick check revealed a website that tracks firefly sightings. According to the Florida listings, there is at least one group of fireflies around in late March to May, and another roughly late June through the first part of August. Adult fireflies live a few weeks to two months, and often feed on nectar from flowers.
Although the only report from Tallahassee suggests the fireflies were out earlier in the year, she potentially could see fireflies in Florida now. So, are they absent because it was a wet year? Knowing a little bit about fireflies, I would say the opposite. They should be more abundant in wetter years and in wetter locations. Why? Fireflies are not flies at all, but actually beetles. As such, they pass through egg, larva, pupa and adult stages. In the larval stage they are eating machines, just eating and growing. The larvae look sort of like elongate tanks, with movable plates on their backs and can glow just like the adults. What do they eat? Depending on the species, firefly larvae eat things like snails, slugs, earthworms and the larvae of other insects, such as cutworms. Most of those things thrive in wet years, so the fireflies should have more food and do better in wet years and wet areas.
What about pesticides? To be honest, I don’t know enough because I don't know what pesticides are used there. The type of pesticide, how it is applied, and where and when it is applied will influence how many other insects will be killed. In general, a broad-spectrum pesticide sprayed for adult mosquitoes would probably kill a lot of non-target insects, including fireflies. In fact, the non-target insects are often more susceptible than the pests.
People have suggested other reasons for decreases in firefly sightings. One is the great increase in light pollution at night. Either the fireflies move to areas with less light pollution or people have more trouble seeing the fireflies (like we have more trouble seeing stars in the sky at night), or both.
Another suggestion is that more people feel unsafe going out at night and stay inside, keeping their doors locked while they watch TV. If you aren’t out looking, you won’t notice if fireflies are active or not.
Without more information, I'm afraid I can't say for sure why there aren't any fireflies in Tallahassee right now. If you have any other ideas, please feel free to share them. If you have time, check when or if fireflies can be found in your area and let me know if you see any. In case you were wondering, even though it is pretty dry here, we do have firefly beetles in the desert. The weird thing is that they don’t glow or flash.
If you would like to encourage more fireflies in your area, you can provide food for them. Simply planting flowers to provide nectar can be a great first step. Many of our cultivated flowers are bred to look nice and may not supply nectar. Look for lists of nectar plants for butterfly gardens, as these will supply nectar for other insects too.
If you want to provide food for the larvae, think about having a compost heap. Earthworms, snails and slugs can all live in the periphery or cooler areas of a compost heap.
Fireflies also do better in forested areas, so plant and encourage trees in your community. Leaving a few dead trees and/or logs in the forest to rot provides homes and food to fireflies and related creatures.
If you turn off excess lights at night it will not only help the environment and save you money, it may help fireflies too.
Finally, this may be obvious, but let fireflies live. If your child puts them in a jar, enjoy them for only a moment and then let them go again. I hate to be a “humbug,” but handling any insect shortens its life through unintentional injury, through the potential spread of diseases when many insects are brought together in cramped containers, and through disruption in the normal behaviors of the insect. Also, discourage others from chasing and killing fireflies with whiffle bats or tennis rackets, often seen as a game.
One of the best ways to encourage fireflies is to learn more about them by reading books and websites. Here are a few:
For a more technical discussion of how fireflies defend themselves with chemicals, try Chapter 4 in Thomas Eisner's Book "For Love of Insects."