The Susquehanna Greenway is aglow this month thanks to the bright lights of this Greenway native and Pennsylvania state insect: the firefly. These small but mighty insects are hallmarks of summer. Their mesmerizing light shows capture the imaginations and the hearts of adventurers the world over, but how much do you really know about these talented creatures?  

They go by many names

If you’re from the New England or the West, you probably refer to them as ‘fireflies,’ but if you’re from the South or the Midwest ‘lightning bug’ is more common. However, these insects are actually not a ‘fly’ nor a ‘bug.’  

They are in fact members of the Lampyridae family of winged beetles; that’s right, they are beetles! The word Lampyridae actually comes from the Greek ‘lampein,’ which means ‘to shine.’ 

They undergo a chemical reaction in their abdomens

This reaction produces their flash, which, depending on the species, can range from yellow, orange, and our favorite–GREEN. While more than 2,000 species bear the name “firefly,” not all of them glow.  

Those that are lucky enough to flash do so by mixing oxygen with a pigment called luciferin to generate light with very little heat. They are actually one of the most efficient energy producers in the natural world.  In fact, almost 100 percent of the energy they produce is emitted as light. Compared to an incandescent light bulb, which only emits 10 percent of its energy as light, that’s pretty incredible.  

Why do they glow?

Fireflies light up mainly to attract a mate. Male fireflies flash while hovering over tall grass or trees. If a female firefly decides she likes the male, she will respond with her own unique series of flashes from lower on the ground.

Since each species of firefly has its own unique flash, it’s important for females to figure out which males are the right ones. A good pick up line, like “you look flashy tonight,” can sometimes help things along.  

They Live Short but En-lightened Lives

The egg to larvae stages of the firefly life cycle last from the end of summer to the spring, after which the small larvae dedicate all their energy to growing wings and hard-shells. Once they emerge as fully-fledged fireflies in the late spring, the small glowing insects only have about two months to find love before their lights go out forever. 

Now that you know some cool firefly facts, the hot humid days of July and August are the perfect time to get outside and watch the light shows. Since fireflies are cold-blooded, hotter weather means their flashes will be longer and brighter.  

Where are the best places to watch fireflies in the Susquehanna Greenway?

We recommend fields with tall grasses and low light pollution. Areas where the grasses meet the forest line offer an ideal dark backdrop for the incandescent glows. The river banks of the Susquehanna are always a great place to catch some bioluminescence.  

Check out our Interactive Map to find a public river access near you, or you can explore our inventory of parks and trails.

This summer, you can also help scientists learn about the geographic distribution of fireflies and what environmental factors impact their abundance through the Firefly Watch Community Science Project. Just pick a spot to observe them, and map them here.

The Susquehanna Greenway is a corridor of connected trails, parks, river access points, and communities, linking people to the natural and cultural treasures of the Susquehanna River. The mission of the Susquehanna Greenway Partnership is to continue to grow the Greenway by building connections along the Susquehanna River, inspiring people to engage with the outdoors, and transforming communities into places where people want to live, work, and explore.