The joys of firefly season (What’s in Your Backyard)

Almost anywhere east of the Rockies, people of my generation share some variation of the same childhood memory. In cities, in suburbs or on farms, a patch of green space was all it took. As dusk fell on long summer evenings, you would notice a spark flashing over the grass. This was answered by another, then another, until the whole yard was alive with tiny flashes of light, “living fireworks” in the words of Sara Lewis in her marvelous book, “Silent Sparks.” 

No child could resist close-up inspection, so chasing lightning bugs was a ritual of growing up. Captured lightning bugs were held in loosely closed fists as we waited for a spark of light in our hands. Some of us gathered them in jars. Many of these luminous beetles didn’t survive the encounter, but there were always hundreds more, reappearing at every sunset for a few magical summer weeks.

The good news is they are still here. The numbers have diminished, but any child or adult who steps outside and looks up from their cellphone on an early July evening in Montclair might still get a taste of the magic.

It’s a romantic spectacle, not just for us but for the lightning bugs. Their show is devoted exclusively to love, or, at least, to sex. For a lightning bug, your yard in the summer twilight is comparable to a singles bar on a Saturday night. 

The males circulate, flashing their lights in hope of a come-hither answering flash from a female. The demure female remains perched near the ground on a blade of grass or a bit of undergrowth, checking out males until she finds a flash to her taste, then coyly flashing back. How does she make her selection amid all the flashy bling? Longer flashes draw her favor.

While human courtship often involves sharing a meal, lightning bugs skip this aspect of date night, of necessity; having no mouths, they can’t eat. So, what fuels the show? The answer lies in the dark, carnivorous lightning bug childhood.

The sparkling, charismatic lightning bug we love is actually the brief final stage of the insect’s life, lasting a few weeks at the most. The rest of their lives – up to two years – were spent as larvae hidden under fallen leaves, decaying logs or in the top layer of humus-rich soil. 

The larvae spend this time doing what the adults cannot: eating.  Their food choices are not very appetizing to human palates. Snails, slugs and earthworms top the menu, the taste for snails and slugs making the larvae a gardener’s allies.

Hatched in late summer, larval lightning bugs gorge through the fall, taking a break to hibernate over the winter, then resuming nonstop feeding in the spring. The cycle usually continues until the following May, when the larvae build the tiny soil shelters where they will pupate. In June, the luminescent adults emerge, no longer hungry but on the prowl for mates.

While the gloomy larval stage of the lightning bug may seem grim compared to its spectacular adulthood, the larvae carry a hint of the magic to come – they glow! But larval lightning bugs are not looking for sex. Their light serves another purpose: They glow in response to disturbance. Like the bright colors of the Monarch butterfly and other poisonous insects and amphibians, the conspicuous glow of lightning bug larvae is a signal to potential predators: Don’t eat me, I’m disgusting. Their foul taste carries on to adulthood. Birds offered larval or adult lightning bugs as food avoid them, vomiting them up if accidentally ingested.

Lightning bugs are not entirely predator-proof; spiders are unfazed by their chemical defenses.  More dramatically, male lightning bugs are often victims of a “femme fatale,” a vampire firefly whose lifestyle could inspire a misogynistic Hollywood movie, possibly starring Glenn Close. This vampire firefly belongs to a distinct species, Photuris, whose females continue eating as adults. Their diet is very specific: the males of our common, beloved Photinus species. 

They use seduction to catch their prey. The femme fatale responds to Photinus male flashes by mimicking the flash of an interested Photinus female. Unsuspecting males, approaching in expectation of love, find themselves embraced – then eaten.

If you sense that lightning bugs are less common now than in your childhood, you are right. A recent Xerces Society study shows declining populations worldwide. Some factors, such as the destruction of habitat due to development, are beyond the control of most Montclair residents. However, there are steps we can take in our own yards to help out. 

Bright outdoor lights obscure the insects’ flashing signals and disrupt mating. Homeowners can help by turning off outdoor lights at night or installing motion-sensitive lighting.

Lawn reduction is another step; adult lightning bugs spend daytime concealed in shrubs, tall ground covers and other perennial plants. Just cutting back on mowing benefits lightning bugs, who prefer to rest on taller grass.  

Indeed, lightning bug preservation is a perfect excuse for saving time and money on yard care. Pesticides, especially when applied to the ground in the form of lawn chemicals, are a particular danger to the larvae during their two-year stay in the soil. 

And lightning bugs are one more reason to leave leaves – or save them for use as mulch or compost. Since these insects often lay their eggs on moist fallen leaves and the larvae live under leaf litter, scouring your yard with a leaf blower wipes out the next generation.

So, if an occasional neighbor, still mired in the previous century’s destructive landscaping conventions, objects to the clover poking up in your untreated and slightly overgrown lawn or last autumn’s leaves lingering under your shrubs, just tell them it’s for the sake of the lightning bugs.

What former child could argue with that?

In “What’s in Your Backyard,” Sanford Sorkin and David Wasmuth alternate writing about the birds and beasts you may see around your house. Wasmuth is a local environmentalist and amateur naturalist. He is a Rutgers environmental steward and the founder of the Montclair Backyard Habitat Project. Seen a bird or animal you want to know more about? Write to us at culture@montclairlocal.news.