Lights out!
HomeHome > Blog > Lights out!

Lights out!

Jul 23, 2023

Aug 26, 2023

PHOTO BY DEBRA BURROWSThis pasture and the fields beyond are often filled with the glow of fireflies on summer evenings.

Over the past several years, many gardeners and homeowners have begun to revamp their landscapes to make them more supportive of pollinators and other wildlife. They are adding native plants, removing harmful invasive species, reducing the use of pesticides and recognizing the need for space that is suitable for habitats. These are welcome changes which can benefit both humans and wildlife. There is something else that concerned homeowners and gardeners can do, and it is literally as simple as flipping a switch.

We’re learning that artificial light at night, sometimes referred to as ALAN, can be disruptive and even deadly for some insects. Let’s look at one example, the firefly (Photuris pennsylvanica), which was designated the official state insect of the Commonwealth of Pennsylvania in 1974. Locally, many of us simply refer to it as a lightning bug. Regardless of what we call it, the firefly has been a familiar sight on summer evenings and a source of fascination for children and adults alike. Fireflies are bioluminescent, which means they can produce light through chemical reactions within their own bodies. I have childhood memories of carefully catching them in a jar and watching them flash and glow. As an adult, I’ve spent many evenings sitting on the deck with my husband watching them floating and twinkling in our pasture as night sets in. Sadly, I’ve recently learned that fireflies may be in danger.

Like many other insects, fireflies are threatened by loss of habitat and the use of pesticides as well as other changes that humans make to the environment. One of those is artificial light at night (ALAN). Nighttime lighting from a variety of sources has grown considerably in recent years as has the use of bright, energy efficient, LED lights. Brilliantly lit signs that flash messages and colorful designs are increasingly common, as is landscape lighting, security lighting and decorative outdoor lighting. While lighting up the night may seem harmless to humans, it can be disastrous for some insects.

There is evidence that, because they are bioluminescent, fireflies may be at risk from the growing prevalence of ALAN. Fireflies use their ability to create light to initiate the mating process. Male fireflies send out flashes of light to attract females, and females respond with flashes of their own, which signal their readiness to mate. It seems they employ a variety of flashing and glowing sequences to communicate, and the timing is important. When artificial

light is present, it disrupts this process and decreases firefly mating. Flashing signals from both males and females diminish and mating declines. Less mating means less fireflies.

Fireflies aren’t the only insects negatively affected by ALAN. We’ve all seen moths flying excitedly around an outdoor light at night. Unfortunately, the result is that they often die of exhaustion, get burned or are consumed by predators that are also attracted to the light. Nighttime lighting can disrupt the ability of some insects to find prey at night, making it difficult for them to hunt for food. These are just a few examples of the negative effects of ALAN on insects. It is becoming increasingly evident that there are many others.

It might be easy to assume that the decline of insects will have little effect on humans, but that is not the case. Insects play a vital role in the web of life on Earth. Without them it would be a barren and nearly lifeless planet. Insects pollinate millions of plants, many of which humans depend upon for food. Some of our most beautiful flowering plants rely upon insects for pollination. Insects, especially when in their larval or caterpillar stage, are a primary source of food for birds, especially baby birds, which are not yet able to consume seeds and need soft food to help them grow to maturity. Without insects, life as we know it would quickly grind to a halt. Protecting them and other wildlife and helping them to thrive will help humans thrive as well.

Fortunately, there is an easy and cost-effective remedy for the problems caused by ALAN in home landscapes. We can simply turn off the lights we really don’t need. Not only is there no cost, there will probably be a cost savings on our electric bills. For example, we humans might enjoy a well-lit patio, porch or pathway, but we can turn off those lights when we have gone inside. Does the patio, porch or pathway really need to be lit up at 3 a.m.? We can turn the lights off manually or purchase a timer to do the job for us. We can also consider motion-activated lights, which will turn on automatically when there is movement in an outside area and turn off when the movement stops. We can also use dimmer lights and shield light fixtures so that they illuminate just the space where light is required.

Each of us can take a few minutes and assess the amount of outdoor lighting that is essential to our homes and landscapes and act accordingly. By limiting our use of ALAN to only the areas and times when it is truly needed, we can help fireflies and many other species of wildlife survive and in so doing, make life better for humans as well.

For additional information about light pollution and its effects on wildlife, please visit and


Debra C. Burrows, PhD is a retired Penn State Extension Educator and a certified Master Gardener. She can be reached at [email protected].

Today's breaking news and more in your inbox

I'm interested in (please check all that apply) Are you a paying subscriber to the newspaper? *