Glow

Of all the eagerly anticipated phenomena that mark the spiraling dance of the seasons, few are as sweet, or received with such delight, as the appearance of lightning bugs in June.

Perhaps you call them fireflies. I grew up calling them lightning bugs. In fact, they are neither flies nor bugs. They are winged beetles, in the order Coleoptera. And for many of us who grew up the Midwest, these seemingly magical insects provided an early-childhood introduction to the joyful exploration of the natural world. Many of us have fond memories of dashing across the lawn, big glass jar in hand, chasing flickering points of light and squealing with anticipation of the capture. And we always knew that we could catch these harmless little insects in our bare hands, examine them closely—in rapt fascination of their eerie rhythmic glow—keep them for a time in our clear glass jars (breathing holes punched in the metal lids), and release them once more into their habitat before we were tucked into bed.

Random Factoid:  A Jamaican term for lightning bug is, “blinkie.”

Random Factoid:  A Jamaican term for lightning bug is, “blinkie.”

Adaptation in nature is nothing less than amazing. Why would a little insect evolve in such a way as to regularly emit such a bright, distinctive glow? The short answer is that they use the light to communicate. And most of that communication is about finding a suitable mate.

There are thousands of species of lightning bugs (or fireflies—I’ll use the terms interchangeably) spread across temperate and tropical areas of the globe, classified within five subfamilies. While there are more than 200 species in North America, curiously enough there are few species that occur west of Kansas. (If you really want to impress your friends visiting here from out west, take them to a firefly show.)

Firefly behavior, color, and habitat preferences vary by species, but in general their bioluminescence is caused by enzyme-induced chemical reactions within specialized cells called photocytes. Reflector cells may intensify and direct the light emitted by the photocytes. Light cast by a firefly is extraordinarily efficient; it is what we call a “cold light” because, unlike most sources of illumination, there is no energy lost as heat.

While some fireflies may emit light to defend their territory or deter predators, what we typically see is a courtship display. Each species presents a distinctive blinking pattern that is unique to that species (although there are a few species that mimic one another as a means of interspecies trickery). Males flash their rhythmic signals in flight while females perch in low vegetation; a female may reflect the male’s flash pattern or she may, at a precise time interval, blink back to the male, signaling her whereabouts; the flashing and blinking typically continue until mating is complete.

The female lays her eggs under the surface of the soil. After about three weeks, the eggs hatch, revealing larvae that are fascinating in appearance:  segmented and armored, looking perhaps like a trilobite or some kind of spiny pillbug. The larvae persist in that form for a year or two before spending about three weeks as pupae, emerging as adults who then live for only 3 or 4 weeks—just long enough to reproduce.

A lightning bug larva is a fearsome sight—at least to its prey.

A lightning bug larva is a fearsome sight—at least to its prey.

It is pleasing to find a field or woodland edge filled with the silent twilight courtship display of fireflies. Even as adults we can be mesmerized by the flashing, dancing patterns of green or yellow points of light, swimming in the mild evening air. And yet, some neighborhoods—even some natural areas—seem to host fewer lightning bugs today than in years past. I haven’t found any published studies that compare population trends over time, but there are anecdotal reports of diminishing numbers.

Most of a firefly’s life is spent in larval form, on or below the surface of the soil where they are susceptible to environmental dangers such as drought, flood, contaminants, and predation. Some of the threats to lightning bugs are decidedly human in origin. Lawn chemicals are especially troublesome:  some can kill firefly larvae outright, and they might also kill the organisms that the larvae need to eat. Artificial lighting can reduce the ability of adult males and females to find each other, so we are encouraged to shut off our lights whenever they are not needed.

Those of us who grew up in suburban neighborhoods here in the Midwest may associate lightning bugs with lawns and the residential landscape, but of course those little beetles were here long before modern humans changed the environment, so what natural habitats would have been their haunts? Reportedly, they prefer moist environments that support low-stature vegetation. I would suppose that sedge meadows, mesic savannas, and the margins of wet prairies would have been their preferred habitats.

The ideal time to witness the firefly display is right around dusk, a little after sunset, at the onset of darkness. Firefly activity diminishes considerably about an hour or two after sunset.

Take my advice. Find a moist prairie, sedge meadow edge, or untreated old field. (If you live in a neighborhood that still has abundant lightning bugs, you can do this at home, although ambient light from the neighbors can interfere with the experience.) Perch yourself comfortably at sundown, and take in the show. Allow a soft focus to guide your steady gaze across the gloaming space in front of you. Turn off your thoughts for a few moments, quieting the internal dialog; with silent mind and open eyes, witness the play at hand… and smile like a child enchanted.

Behold, the Box Elder Bug

“You have bugs on your window,” a second grader said very quietly to me the other day, pointing at the windows behind me in our classroom.  I turned and looked, and she was right, the windows were crawling with red and black insects, but there were far fewer than there had been! 

Image from abcwildlife.com

Image from abcwildlife.com

Severson Dells is not alone when it comes to the annual invasion of box elder bugs (BEBs).  Members of the True Bug Family (Hemiptera), these stunningly colored black and red insects are the bane of many a home-owner when fall arrives.  Why are they here, what do they want, and why won’t they leave us alone?

Like with so many animals that have been labeled as “pests” in the eyes of humanity, our troubles with box elder bugs are ultimately our own fault.  Left to their own devices, they would be perfectly happy to leave us alone (see paragraph seven).

Box elder bugs, Boisea trivittata, are one of our native insects (bet you didn’t see that coming).  The family to which they belong, Rhopalidae, is known as the scentless plant bug family.  Its members are notorious for lacking the scent gland that is found on the hind legs of most true bugs.  However, unlike the rest of its kin, the BEB is not unscented.  In fact, it is apparently famous for its stink, which it produces only when pestered – no doubt it is part of its defense mechanism.  Biologists theorize that the production of this smell, and subsequent bad taste, is what allows BEBs to congregate in such large numbers in the fall without fear of being eaten.  The red and black coloring no doubt serves to advertise that it is not tasty, just like the coloration of ladybugs, milkweed bugs and monarch butterflies.

In the spring, the females lay their bright yellow eggs in the crevices of bark of the box elder tree.  The eggs turn red as the embryo develops, and within two weeks the youngster emerges.  Also red and black, just like its parents, the juvenile goes through several instars as a nymph before finally turning into an adult.  All the while, it is feeding on its host plant.  (Like aphids, BEBs have piercing and sucking mouthparts, designed to stab into the “flesh” of the plant on which they feed and suck out its juice.  The food of choice for BEBs is the seeds of the box elder tree, although they are also known to nip and sip from the tree’s leaves, flowers, and tender twigs.) 

So, summer arrives, the nymphs grow and eat, and eat and grow.  All good things must come to an end, however, and soon summer turns in to fall.  As the cooler weather approaches, the BEBs seek someplace new to live.  Remember I said that if left to their own devices, BEBs would happily not have any interactions with us?  It’s true.  In the wild, minus the presence of humans, these insects seek out rocks, loose bark, or hollow logs to crawl into or underneath for the winter.  If it is dry and sheltered, they will be happy.  People, however, have moved in to their habitats, and as we have altered the landscape, BEBs, like so many other animals, have had to adapt.  And lo! and behold – our houses provide dry, sheltered spaces that are just perfect for these insects to overwinter!  In they come – through cracks in the foundation, holes by utility wires or plumbing, old window screens.  They crawl under siding, and nestle by loose windows.  South- and west-facing walls are preferred real estate, for they get good and toasty on cool days when the sun is out.

BEBs are not going to hurt you and are not going to eat your wiring.  If your dog or cat tries to eat them, your pet may get sick, but I haven’t read of any accounts where a pet died after ingesting a BEB.  On the other hand, I have read that even though BEBs do not “bite people,” they have been known to inflict injury, although more as a defense mechanism (you rolled over on one in your sleep) than as a premeditated action (like a mosquito biting you for a blood meal).

So what is one to do when the BEBs seem like they are taking over one’s house?  Vacuum up the interlopers.  You could also employ a variety of sprays, from insecticides to mixtures of water and dish soap, but remember:  insecticides are poisons, and they are not often specific in their targets.  You are better off trying to prevent the insects from invading by plugging all possible entrances during the summer while they are out.  Replace old or torn screens; plug holes with tight wire mesh; put tight screens on foundation and attic vents; be liberal in your caulking adventures.

In the meantime, BEBs could make for some interesting insect studies.  Maybe you can capture and mark some – follow the daily lives of individuals.  Host BEB races for your friends and relatives.  Apply some engineering and see if you can build a better BEB trap!  Who knows – maybe you or your child might discover some previously unknown trait of BEBs that will change the world!