By Justin Isherwood

Sara Lewis of Tufts University in her book Silent Sparks relates how the world’s firefly populations are dwindling. The result of habitat loss, pesticides and rather ironically light pollution.

To start with the basics, what exactly is firefly habitat? According to Prof. Lewis the specific habitat begins with something we might call worshipful darkness. The kind of darkness modern cultures ignore and correspondingly continue to lose with more clever ways. To include here those popular and cheap solar powered LEDs, by which we adorn and light our homes and backyards. According to Prof. Lewis, continually adding light to our personal environs may have a dark side. Make that the other dark side of light pollution.

Fireflies in their well-noted courtship depend on light signals to find true love. This also how I remember the business. The North American contingent of the firefly has some 150 species of 16 genera, divided into three defining groups of light signal; fireflies that flash (my personal preference, a sentiment to be expected of the kilt-wearer), fireflies that glow, and fireflies that use pheromones. There are five genera of fireflies under Lampyridae, the kind that flash, Photinus, 34 species, Pyractomena 16 species, Photuris 22+ species, Micronaspis of salt marshes one specie, and Bicellonycha, resident of Arizona’s middle altitudes 4 and 6,000 feet, one specie.

The light signal of a firefly comes from a chemical reaction producing light that is found with some regularity in nature, glow worms, foxfire, the light emitting fungus (Omphalotus mushrooms) and many sea creatures to include squid, jellyfish, sea spiders and plankton. The light reaction occurs when an enzyme appropriately called luciferase acts on a mutual enzyme called luciferin together in the presence of ionic magnesium, adenine triphosphate and oxygen.

The light signal of fireflies is called cold light because it possesses no infrared signal, no heat. The light is described as yellow, green, pale red, with wave lengths of 510 to 670 nanometers in case you were wondering.
The firefly after mating, whether this is in mid-air I haven’t researched but hoping to try myself, the female lays the fertile eggs on or just below the ground. Depending on temperature, three to four weeks later the eggs hatch, the larva feed in the ground the remainder of summer, then burrow deeper into sod or debris where they over-winter in the larval form.

To emerge in the spring, pupate from one to three weeks, then on an evening in June/July emerge as winged adults, pretty much as the Good Book says. The firefly diet varies by specie, some feed on pollen and nectar, others on larvae, snails, slugs, angleworms. Birds tend to refrain from eating fireflies because they contain a toxin similar to poisonous toads. Besides, it’s dark, the primary defense of nighttime insects. Fireflies in larval form also glow.

The gene for firefly bioluminescence is regularly used to follow and prove genetic transfer in research. With CRISPR this will one day soon be available from local pharmacies as a beauty care option. As to which parts will be designed to glow in the dark being the consumer-option.

Firefly flash patterns are thought to identify both the species and indicative of the mating quality of the suitor. If you have any doubts how this works you only have to see what sunburn array of driving lights can be attached to a pickup truck, that make a pickup truck ignite waste paper and window curtains in its path. This practice turns up routinely among juvenile males with a predominance of farm plates and the Righteous Brothers turned up loud. As any researcher knows to suspect it’s something about breeding prowess.

Science seems to suggest domestic urban lighting may be getting in the way of firefly love. Confusing the signals such that female fireflies are falling in love with patio lights and the increasing array of glowing garden decor.
As for the role of pesticides and fireflies, that plot is pretty straightforward. When lawn care routinely includes insecticide for mosquito control and systemics that impact earthworm and slug production in urban gardens, coincidentally the food source of larval fireflies.

What is most problematic is the very image of the modern suburban home, and the absence of a key firefly element, debris, that certain vegetative clutter, brush piles, woody ground tissue, tall grass, leaves. Tidy being the antithesis of firefly habitat and here the consummate expression of the suburban home. Firefly habitat isn’t tidy. Instead a complex of tall unmown grass, dense shrubs and a distinct mushroomy damp. Bark and leaves left on the ground is a firefly larval site, slugs like this too, as do earthworms. Firefly mating occurs in the still air of the woody copse, in and under trees, in the slow air of brushy plants and haphazard debris. The very elements the modern suburban home eliminates, in turn the bare ingredients of a firefly night.

Worldwide there are some 2000 species of fireflies, most are at risk. Firefly numbers diminish on a world scale as civilization continues to clean up its act; the elegant well-mowed lawns, professional lawn care, the municipal brush pickup. Lacking is that essential clutter. A corner space left a touch more natural, to include a bit of third-world trashiness, a place where the wild things grow just might do the firefly a favor.
So next time you want to clean the place up a bit … don’t.