Miss Manners would croak.

The southwestern family in "Coyote Ugly," the second import in the Kennedy Center's summer showcase of Chicago theater, makes the dimwitted and lascivious creatures of "Tobacco Road" look like models of couth.

When Ma, a slattern in dirty underpants, gets hungry, she rustles up a can of whipped topping and sprays it directly into her mouth. Pa, a drunken reprobate perpetually in heat, paws any female in sight. ("Why," Ma suggests indelicately, "don't you go rub yourself up against an appliance for a while?") Sis, who gives new meaning to adolescent rebellion, spits in Ma's face every time she passes. And that, I warn you, is just the beginning.

Lynn Siefert's play, which opened Saturday night in the Terrace Theatre, has been mounted with unapologetic zest by the Steppenwolf Theatre Company. The five actors aren't merely sinking to the lower depths, they're diving in head first. Under the circumstances, it does seem the thing to do. If you're going to slum, you slum; restraint would be unseemly.

Until the excesses begin to pale simply by force of repetition, which is about halfway through "Coyote Ugly," the production actually imparts a perverse sense of exhilaration. It comes more from the derring-do of the performers than the script itself, which could be described as a blend of Sam Shepard's "Buried Child" and the gross-out films of John Waters. But there's a giddiness to the squalor, a feeling of low revelry, that some sensibilities may find entertaining -- those, I hasten to add, not necessarily put off by the sight of an actress biting off the head of a dead fish.

It is far less rewarding to view "Coyote Ugly" in any other terms, although Siefert's play is fairly rank with greater meanings about the call of the wild and the sharp, crippling talons of the family. Twelve years ago, Dowd, the son, fled this nest, as he puts it, "to join up." "The Army?" asks Ma. "The human race," he replies. Now that he's back for a visit with his wide-eyed bride, it's as if he never went away. The tentacles of insanity, scurrility and incest that bind this clan together reach out and reclaim him. Ma knows best: "There's more to gettin' out than leavin', " she says.

In its themes and structure, "Coyote Ugly" is, in fact, rather too close to "Buried Child" for comfort. Setting her play in a patch of Arizona desert, littered with the symbolic wreckage of 20th-century civilization, Siefert also seems to be echoing Shepard's vision of the Southwest as a landscape of dying myths. However, when she is not straining for deeper resonance and is willing to let her characters luxuriate in their base stupidity, she can write distinctly original dialogue. "The Grand Canyon is nothing," Pa observes with the scorn of one too shiftless to pursue his wanderlust. "You're just paying for a name."

By exploiting the rowdiness of the spectacle, director John Malkovich manages to mask some of the play's sillier intellectual pretensions. Indeed, the cast members would all do Soupy Sales proud, as they douse one another with warm beer and cold milk; hurl about fistfuls of flour and sand; and engage in sundry acts of punch-drunk pinching and passionate pummeling. Cartoons on the loose, they are constantly whipping up the red dirt that covers Kevin Rigdon's set into mushrooms of atomic dust. That takes a combination of guts and energy, and this cast has both.

Moira Harris builds the mother out of sloth, anger, dementia and sweaty desire. The very boldness of her performance often makes a repugnant character wildly funny and, sometimes, nearly human. Laurie Metcalf explodes with all the warring impulses of the daughter, in whom the family demons are further exacerbated by the contrariness of adolescence. I don't know that I ever fully believed Frances Guinan (the beer-swilling father), Randall Arney (the prodigal son) or Kathleen Sykora (the traumatized bride), but I appreciated their zeal under duress.

A little of "Coyote Ugly" goes a long way. And two acts is a longer distance than some spectators will want to travel. Still, I'll grant the piece the courage of its recklessness. Casting proprieties and caution to the wind, it rubs our noses in muck and madness. Gleefully.

Coyote Ugly, by Lynn Siefert. Directed by John Malkovich. Sets and lights, Kevin Rigdon; sound, Gregg M. Winters. With Randall Arney, Francis Guinan, Moira Harris, Laurie Metcalf, Kathleen Sykora. At the Terrace Theater through July 6.