By Elizabeth Royte

Why do weeping willows weep?
— Clay Wilwol, Frankfort, Kentucky

The droopy willow has been an oft-cited metaphor for sorrow since biblical times. ("By the rivers of Babylon ... we wept [and] hanged our harps upon the willows," Psalms 137.) During World War I, Claude Monet painted a famous series of weepers to symbolize the French nation in mourning. But why the hangdog expression? "They're depressed?" suggests Frank Santamour, eminent tree geneticist at Washington, D.C.'s National Arboretum, before confessing, "No one knows why. Their branches have never been studied at the cellular level." Despite the mysterious sagging boughs, one thing's certain: It's a tree that's been known to make people weep. Willows may look harmless as their leafy tendrils sway lugubriously in the breeze, but beneath the ground they're all business. "Their fibrous roots are extremely aggressive," explains Nick Gawel, a plant DNA expert at Tennessee State University. "They can ruin your septic system and your pipes. They're a disaster!"

Why are moths drawn to light and what do they get out of it?
— Emily Allen, Waco, Texas

Despite the old adage, "like a moth to a flame," moths aren't the only insects that gravitate toward light; they're simply more active at night than wasps and beetles and thus appear more lamp-obsessed. That said, the moth, specifically the male moth, is attracted to an illuminated lightbulb for the sad but simple reason that it thinks it's the Moon. For roughly 150 million years, the visually impaired lepidopterans relied on the giant orb to help them navigate in a straight line, always keeping the Moon's rays at a constant angle during their nightly mating flights — flying a more or less steady course until they caught the scent of a female perched on a nearby leaf. But moth history took an unfortunate twist when the incandescent lamp arrived on the scene in 1879. "Moths will never forgive Thomas Edison," says Cornell University entomologist Cole Gilbert, noting that chaos ensued as the nocturnal creatures began mistaking lightbulbs for the Moon. Unfortunately, flying so close to these surrogate moons makes it nearly impossible for a moth to maintain a straight course, so it must constantly correct its bearing. "Before you know it," says Gilbert, "the poor guy is fluttering around in circles." Relief comes only when the hapless moth resigns itself to a celibate night on a strange porch, waiting until dawn, when it can find its way home — or fly indoors and exact sweet revenge on your sweaters.

A past Wild File column explained the difference between a stream and a creek. But what distinguishes a pond from a lake?
— Bob Wilson, Atlanta, Georgia

Not a thing, at least not officially. According to the experts at the U.S. Board on Geographic Names, whose job it is to approve place names that appear on federal maps, all "natural bodies of inland water" are lakes — regardless of size. In other words, "lake" is the Board's generic term. But we don't live in a generic world, and in deference to that happy fact, the Board recognizes 54 different varieties of lakes, including basins, backwaters, and yes, ponds. Among the more obscure entries on the list are the charco, an intermittent pool found in Oregon and Texas; Utah's guzzler, a flooded area close to a stream; and Central Park's northernmost body of water, the Meer. Ultimately, the difference between a lake and a pond is in the eye of the original namer. "It's a very subjective and emotional process," says executive secretary Roger Payne, who is quick to add that there are 95 federally recognized Big Ponds and 1,366 Little Lakes in this country. "We're not here to question people's logic."

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