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Good Natured: Moths can provide an eye-catching display

Published: Friday, June 6, 2014 10:49 p.m. CDT
Caption
(Photo provided)
Underwing moths are named for their brightly colored hindwings, which typically are kept hidden until the moth takes flight.

Seeing as it’s June, the most popular month for weddings, it seems fitting that we talk about ... moths.

I’m sure you’re probably thinking, “Moths? Eww. Aren’t they the critters that eat my wool sweaters and hatch out of my birdseed?” Well, yes, but that’s a topic for another time. Many other fine species – more than 11,500 in North America alone – live among us and lead wonderfully rich lives full of mystery and intrigue.

Underwing moths (Catocala species) are no exception.

Let’s start with that fancy genus name. Hidden therein, disguised amid Greek roots, lies a clue to the underwings’ great claim to fame. Cato is derived from kato, which means below or behind. And cala is from kalos, for beautiful.

Taken literally, the underwing moth has a beautiful behind.

But if we left the story at that, we’d be creating entirely the wrong impression. What the word really refers to is the moth’s hindwings – the ones that sit, completely concealed, beneath the forewings when the creature is at rest.

Sitting quietly on a tree trunk, underwing moths are some of our area’s best-camouflaged members of Class Insecta. Their elaborately marked forewings look just like bark; in fact, some even look like bark speckled with lichens or moss. But the real show starts when an underwing is disturbed and/or takes flight. That beautiful behind is revealed and, depending on species, flashes brilliant hues of yellow, orange or red, as well as black or white.

Such an eye-catching display is startling to say the least. For an underwing being pursued by a predator, that surprise splash of color may buy the moth the split-second it needs to avoid capture. Alternatively, it can serve to bring interested naturalists closer, in hopes of making an identification.

You see, another cool thing about underwing moths is their common names. Long ago, the Swedish taxonomist Carl Linnaeus came up with the idea of naming underwings using a theme of women and relationships. He gave us the names of the European species C. nupta, (“marriage”) C. pacta (“agreement”) and C. sponsa (“wife”). Other scientists followed suit, and today we have names like the girlfriend, darling, sweetheart and betrothed; the bride, once-married, mother and old wife; and the tearful, gloomy, inconsolable and widow underwings.

Some are named after women known for their beguiling ways, notably Cleopatra and Delilah. And some are named after Shakespearean characters, such as Ophelia, Miranda and Desdemona.

Want to take a closer look? Sneaking up on an unsuspecting underwing is harder than it sounds. For one thing, if they’re resting on tree bark, they’re next to impossible to spot – even though their beefy bodies may measure nearly 2 inches in length. Luckily, they at times come to rest on fence posts or rocks where their camouflage isn’t as effective.

For another thing, underwing moths have extremely good hearing. They’re very hard to approach and often take flight long before you’re close enough to make even a tentative identification. Their “ears,” tympanic membranes on either side of the thorax, are quite sensitive and can pick up sound even in very high-frequency ranges; it makes things tough for us nature nerds, but it’s definitely a handy trait for these moths, who frequently must elude hungry, echolocating bats.

Right now the underwings in our area are caterpillars, having overwintered as eggs and hatched out earlier this spring. In another month or so they will pupate, emerging as adults in late summer or early fall. And that’s when the fun, for naturalists, really begins.

If you’re up for some delightfully nerdy entertainment, make a note to head out to a woodsy natural area on a warm, humid evening this September. St. Charles’ Norris Woods is a good choice, as is the Hickory Knolls Natural Area. Bring along a set of keys.

At Norris, quietly inspect the posts of the interpretive kiosk by the parking lot. At Hickory Knolls, shine a light in the fireplace at the picnic pavilion. Chances are fair to middling at either of these locations that you’ll encounter an underwing at rest.

A puff of air, or maybe even just your sustained presence, will send the moth aflutter.

As it wavers its way toward the refuge of the trees, give your keys a shake. The metallic jingling sounds have an ultrasonic component that emulates those of bat sonar waves. When the underwing senses this sound, it will drop from flight in defense. Neat, huh?

Oh, and if anyone asks what you’re doing, just say you’re out having some snicks and giggles with your sweetheart. Or darling. Or old wife …

• Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at potto@stcparks.org or 630-513-4346.

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