June Fireflies on Wild About Utah

Jun 23, 2017

Most people are fascinated by unusual displays of light.  Meteor showers, solar eclipses, and the stunning Aurora Borealis, or Northern Lights, are grandiose in scale and mesmerize onlookers.  But people are also enchanted with the small life-forms that create their own light.

Bioluminescence, the production of light by living creatures, is an incredible phenomenon produced by certain mushrooms, scorpions, millipedes, bacteria, snails, worms, beetles, and nearly half of marine life including single-celled plankton, jellyfish, octopi, and fish.  Some are also fluorescent by absorbing light rays and then emitting them as a different color.

But today we will focus on fireflies, also known as lightning bugs, which are actually beetles.

How, and why, do these creatures produce their own light?  Scientists are still learning how the process works, but basically it is a chemical reaction involving luciferin, a light-emitting compound, being catalyzed by an enzyme and reacting with oxygen to release cool, light photons. 

The “why” part is primarily for locating mates.  But other species could also use it to lure prey, as a method of escape, and to warn predators.

The nighttime hours of late Spring and early Summer months are prime time for firefly activity.  They live around wetland areas where the soil is moist and will start flashing when the sky is dark.  Females remain fairly stationary atop tall grass and watch for males who fly around flashing various light signals.  When a female approves of a suitor’s signal, she will respond with her own glow pattern which allows the male to find her.  After mating, the female will lay eggs in the moist soil or leaf litter where they won’t dry out.  The eggs usually hatch in 3-4 weeks.

The larvae live in the soil hunting worms, snails or slugs.  At this stage they may actually begin glowing.  They live in the soil for one or two winters before pupating and undergoing metamorphosis into the adult stage.  And the purpose of the adult stage is primarily breeding.

While we enjoy seeing these insect “shooting stars” it is critical to avoid trying to capture them since the Utah populations are small and fragile.  (Photos are available online on many websites if one needs to see them closeup.)  Walking on the soil can kill the eggs or larvae, and light from automobiles, street lights and flashlights can disrupt their ability to see the flashing of their prospective mates.  While the “Firefly Citizen-Science Project” from the Natural History Museum of Utah indicates sightings at more than 50 locations, careless actions, as well as loss of critical habitat, are actually causing a decrease in populations across the country.

Let’s do our best to be good stewards of the earth and only “observe” the amazing firefly.