Every beam of slanting light, every breath of wind, every flitter of movement revealed something unseen. A droplet of rain splashed on the deck, a potential marvel of aquatic life. A newly noticed stain on the fence proved to be a burgeoning lichen. A squirrel ran into the yard and paused to scratch itself, prompting Merrill to yell out: “Squirrel fleas! New yard species!”

And it was clear that many more species were going by— in the night sky, in a robin’s intestine, hiding under a leaf, silently creeping past — that we were missing entirely.

In hopes of seeing more, I installed a device known as a dripper, which creates the plink-plink sound of fresh water that is supposedly irresistible to many bird species that would never deign to visit a seed or suet feeder. Sure enough, as the spring migration moved through, gorgeous jewel-colored species known as warblers, of a sort we’d never seen in our yard, dropped right out of the sky to drink, bathe and frolic.

Amazed by these visits, we began to fantasize about what else we could bring in by displaying other enticing items — cut fruit, fresh steaks, rotting fish, a chattery bird, a live mouse. Out of respect for our neighbors, not to mention the feelings of the chattery bird and the mouse, we opted against hanging anything but laundry on the laundry line. Still, we wondered what we might be missing. A peregrine falcon? A snowy owl? The cougar that hadn’t been seen on the street since it stalked the newspaper carrier several years ago?

One night, Merrill hung up a black light, which uses the same bulb that gives that magical purple glow to black velvet posters. It also attracts insects, and by morning a whole new world of nocturnal life was revealed to us. The attached trap held many more species of moth than we had seen before. There was even a water boatman, an insect named for the canoelike body with which it paddles about in streams or ponds — even though there was neither stream nor pond near us.

I wish I could give you a bottom-line species count, but I can’t. Living organisms are reliably, inspiringly unpredictable, as any birdwatcher can attest; in years of watching, we have seen many species only once, so it is very likely we have missed many more. And though we are good at spotting birds and insects, we are nearly plant-blind, so who can say what botanical change has been afoot here? The same is true for the many, many microscopic things we literally cannot see.

And that moth that I was the first to see alive in North America? Actually, I’m virtually certain I wasn’t the first. It was the first live Oecophora to be identified on this continent, perhaps, but others had been found dead in traps and live ones were spotted elsewhere soon after. In fact, earlier on the very day that Merrill caught the moth at our house, my daughter’s friend pointed out a colorful moth that might well have been Oecophora. For those, like children, with eyes open wide, rarities can abound.

On any given day, of course, you’re not likely to spot an unexpected guest. But one day it will happen. While you slice a grapefruit or fold laundry or sit at the computer, something unbelievable will be creeping or flittering through your life. Look for it, just in case.