BETHLEHEM, Pa. — With summer arriving on Thursday, fireflies have started to sparkle across lawns and fields in the Lehigh Valley — and there are plenty to see.
“Here, we can easily observe many different firefly species — each species has its own unique flash pattern,” Muhlenberg College biology professor Marten Edwards said.
“Some flash only at dusk, while others are active late at night.
“My personal favorites are the ones that make a distinctive J-shaped flash a couple of feet off the ground. Even the color of their flash can vary between species.
"Notice the ones that flash late at night; they twinkle high up in the tree canopy and emit a brighter shade of green.”
With more than two dozen species of fireflies that call Pennsylvania home, it’s no wonder one was adopted as the state’s insect.
A hallmark of summer across the region, with behavior considered the genesis of the fatal attraction, the flashy insects are threatened because of habitat loss and light pollution.
However, Edwards said residents can help by ditching lawn and garden chemicals, as well as leaving the leaves.
“Our state insect, the Pennsylvania Firefly — Photuris pensylvanica — requires a particular wetland habitat, so it is declining primarily due to habitat loss," said Edwards, who also is chairman of Muhlenberg’s biology department.
"Light pollution is a significant threat to other species because the males and females need to find each other by recognizing each other’s flash, which gets drowned out by city lights.
“Imagine trying to respond to a distant whisper at a Metallica concert.”
Here's LehighValleyNews.com’s interview with Edwards. Some answers were edited for style and clarity.
Q: Is there a difference between lightning bugs and fireflies?
A: Lightning bugs and fireflies are the same thing. Technically, they are not bugs or flies, either. They are a kind of beetle.
Q: Do we know how this insect got its name?
A: They get their name because many species of this family of beetles communicate with a chemical reaction that produces light.
Q: Why do they light up?
A: When they are in the larval stage, they are thought to produce light to warn potential predators that they taste horrible.
As adults, the males light up to impress females with their flashing skills. Each species makes a distinctive flash. If a female of the same species likes his flash, she will respond with her own “come hither” flash, and this will attract the male.
One firefly species generally doesn’t respond to another’s flash — unless it is a female of a species that attracts a male of a different species by imitating the female flash pattern of that species and then capturing the unlucky suitor and eating him!
This is where the concept of “fatal attraction” came from.
Interestingly, our Pennsylvania state insect — the Pennsylvania firefly — is one where the females feast on the males of another species (but give the males of their own species a free pass).
Not all fireflies produce light! Some are active during the day and communicate with each other using chemical perfumes. I grew up in Washington State, where they have many species of fireflies — but none of them produce light.
Q: Are there other insects that light up?
A: Here in the Lehigh Valley, the most common flying flashers are fireflies. Though firefly larvae can produce light, there is another kind of beetle that lives in Pennsylvania that also produces light as larvae — for this reason, they are called glow worms (but they are not worms). Other beetles produce light as adults in other places. For example, the “fireflies” you will see in Miami, Florida., are actually a kind of click beetle.
Q: What does their life cycle look like?
A: Their larvae are generally predators and live in the soil or leaf litter. They are generally predators of other insects at this stage. Most species spend the winter in the soil or the leaf litter and then go through the pupa stage in the late spring and emerge as adults in the summer when we see them. Since the larvae live at the ground level, it is a good idea not to remove all of the leaves and it’s why it’s never a good idea to put grub killer on the lawn. Grubs are also beetles, so when you kill the lawn grubs with insecticides, you also kill the fireflies.
Q: Where are they situated in the food chain (who eats them and who do they eat)?
A: Most species are predators of other insects and do most of their feeding as larvae. Most of the fireflies we see do not eat as adults, except those that eat the males of other species.
Q: Are fireflies nocturnal?
A: The ones we see flashing are nocturnal and rest during the day. However, the ones that communicate by smell are active during the daytime and don’t flash.
Q: Where are they most likely to be found in the Lehigh Valley?
A: They are common in most natural areas and gardens, especially where people don’t use pesticides in their lawns and gardens.
Q: What threats do they face?
A: There are about 30 different species of fireflies in Pennsylvania. Each species has its own needs. The Pennsylvania Firefly requires a particular wetland habitat, so it is declining primarily due to habitat loss.
Some species seem to cope with our light pollution — but no species can deal with the chemicals we put into lawns and gardens. In the urban setting, that will be their biggest threat.
Q: What can residents do to help bolster firefly populations?
A: The easiest and most important thing you can do for the fireflies (and other important beneficial insects) is to stop using lawn and garden chemicals. It is possible to have a fabulous lawn and garden without killing the insects that bring so much magic to summer evenings!
The other thing we can do is stop raking every last leaf and resist the urge to remove all dead vegetation from the yard each fall. Leaf litter and other decaying plant material help the soil and provide a habitat for fireflies and many other beneficial insects. I've found that it's possible to create a healthy firefly habitat without making the garden look messy at all. Fortunately, here in Pennsylvania, there are opportunities for firefly Citizen Science, and true enthusiasts can even participate in the famous Pa. Firefly Festival.
Q: I remember collecting and jarring up fireflies when I was a kid. With these insects threatened, is it best not to do that?
A: If it were up to them, they'd prefer to be left alone — but compared to all the threats they face — this is the least of their problems.
Putting a few fireflies in a jar and admiring them up close is a marvelous idea! Just put some vegetation in the jar to keep the moisture levels high enough, and screw the lid on loosely to allow some airflow. Let them go after the kids have gone to sleep (they’ll forgive you), so the next night, they can flash with their friends.
It’s never been more important for kids of all ages to appreciate the importance of the natural world that surrounds us, and fireflies are a fun way to build that timeless connection.
