Something wonderful happens from time-to-time in parts of Appalachia. It is a natural phenomenon that seems to occur in early fall, when the heat of late summer still persists but the length of days shortens.

Scientists are not exactly sure why it happens. Seems to be a migration of sorts, but birds aren’t the creatures congregating in miles-wide clouds visible on radar screens.

The National Weather Service (NWS) tweeted radar images taken on Sept. 10 that showed vast clouds of dragonflies sweeping like rain storms over six states. The occurrence warranted coverage in The Washington Post when the swarming insects passed over on parts of Virginia, Maryland and New Jersey, perhaps even flying high over Washington, D.C.

The millions of insects massed thickly enough to reflect on radar as swirling storm cells. According to entomologists, such huge congregations of dragonflies high in the air aren’t unheard of and might occur due to weather conditions or in response to concentrated swarms of prey animals, such as gnats, flies and other small insects.

The exact reason for these dragonfly swarms is unknown, but for the earthbound observer the occurrence is something never to be forgotten. Imagine thousands of metallic green-and-blue dragon flies, interspersed with brown-bodied and bronze-winged fliers, hovering and darting around and above you—everywhere you look—but never actually making contact.

When my family lived in southeastern Ohio, a part of Appalachia, I awoke from a nap one Sunday afternoon to find light and shadow twinkling on the wall of the den. Peeking out the window, I beheld a myriad of flying insects dipping and diving over our garden and flower beds. In fact, the swarm coiled upward like a living dust devil to funnel over the mountains. Dragonflies, perhaps billions.

I was astounded. My wife and I walked outside. We were enveloped by insects, but the individual dragonflies deftly avoided collision with us. A thundershower had passed through and the air was humid for early September. It seemed the dragonflies were feeding on something, mosquitoes or midges, perhaps. But I can’t prove it.

In turn, the flitting insect predators themselves were targets. The mockingbirds, blue jays, blue birds, redwing blackbirds and wild sparrows gorged. Even crows found the sudden dragonfly buffet irresistible.

My wife’s chickens in their pen chased and caught the swarming insects. It was a smorgasbord for wild animals, including crawfish that scuttled from their holes to pounce on insects knocked from the sky by diving birds and the orb-weaving spiders whose webs were ripped to tatters by the weight of trapped dragonflies.

Cars and truck drove past our farmhouse with wipers smearing smashed dragonflies on windshields. Horses cavorted and kicked in pastures; cattle sought shelter in the woods; and fish jumped and flopped in ponds as they tried to catch dinner.

Finally, as if in response to a signal, the swarm dissipated at ground level and the cloud swirled off to the southeast toward the Ohio River. They were gone as suddenly as the dragonfly migration had appeared. Perhaps the insects had been attracted by a hatch of smaller bugs from the creek that ran through my farm. Maybe it was the moist air funneling between the mountains. It never happened again. I am grateful we witnessed this miracle of God’s nature at least once.

The best way I can describe the experience was being cocooned in a rainbow, while your ears registered the susurration of diaphanous wings numbering in the millions. A sound like angel wings might make, and each insect reflecting prismatic color that caused twinkles through the window of a dark room.

ν Steve Oden is an award-winning columnist and former newspaper editor. He resides in Tennessee.