In the interest of giving credit where credit's due, let me first mention that Mimic has great bugs. Under the supervision of longtime SFX maestro Rob Bottin (Se7en, John Carpenter's The Thing), this film's swarm of giant, mutated cockroaches is ravishingly sickening. One shot in particular, which you may have seen when star Mira Sorvino appeared on the Letterman show, is so crazy and startling that it had the audience at my screening breaking into applause. Mimic is evidence that inspired special effects can be their own reward. (Bottin's directorial debut will be, um, Freddy vs. Jason, which pits the epochal slashers of the Friday the 13th and Nightmare on Elm Street series against each other, presumably en route to Hell.)

But if you guessed that the bugs are the only good news, you're right. Mimic starts out as a pedestrian thriller and deteriorates slowly into a depressingly bad one. It's not without a few good sequences, and director Guillermo del Toro once again exhibits a great respect for the genre. (Ole Bornedal, whose remake of his own Nightwatch has been sitting on Miramax's shelf for close to a year now, has a producer credit!) But in the end, Mimic turns out to be an apt title for a film that shamelessly snitches its best ideas from better pictures.

Sorvino plays Susan Tyler, a brilliant scientist who, in a prologue, engineers a new "Judas" breed of cockroach to wipe out more traditional New York roaches who have been spreading a deadly disease that attacks children. Three years later, the story picks up as two street urchins sell Susan an impossibly big specimin of cockroach they found at the Delancey Street subway station. No dummy, Susan doesn't waste time deducing that her genetically engineered roaches didn't die out exactly as they were supposed to. Somewhere beneath Manhattan, there's a whole colony of these resilient little buggers, which could spell big trouble for humanity.

So Susan and her husband Peter (Jeremy Northam; they're trying, unsuccessfully, to get her pregnant) venture underground to investigate. Stupidly, Peter goes deep with only buddy Josh Brolin and a cranky transit cop (Charles S. Dutton) for support. Also involved are a shoeshine man (Giancarlo Giannini) and his son (Alexander Goodwin), who can tell the size and style of somebody's shoes just by listening to them, and who learns to mimic the sounds of the big insects.

Del Toro helmed Cronos (released in the U.S. in 1994), which was a fairly interesting Mexican riff on the vampire legend, but he's a lot farther from home this time. The more conventional Mimic moves fitfully, with bracing special effects sequences that are pretty much counter-balanced by the leaden pacing of the stuff in between. For the first half, we're interested enough in learning as much as we can about these critters that the film's herky-jerk rhythms are almost pleasantly off-putting. And the pay-off scenes tend to be creepy-crawly doozies, with ugly little cockroaches leading the way to more distressing looking big ones. (Who is that guy in the trenchcoat, anyway?) The obvious ancestor is Alien, which relocated the slasher movie to outer space. But Mimic has more in common with your garden variety slasher film, where clumsy exposition and character development always lead up to a centerpiece sequence of flesh-ripping, than with Alien's more challenging SF metaphors.

When two of the heroes find themselves isolated in a long-abandoned underground subway terminal, it becomes apparent that del Toro is most assuredly not much of an action director. So Mimic winds down into a tedious cramped-quarters thriller that has so little sense of character that nothing at all seems to be in jeopardy. There's no sense of place, either. For all its reliance on the threat of an infested subway system, Mimic has as much New York ambiance as Rumble in the Bronx -- that is, none at all. All that remains is to watch the characters sacrifice themselves for one another in tag-team fashion. (Sorvino even gets to mar her hand with a symbolic stigmata.) Still, the ending is pretty upbeat. Even though F. Murray Abraham, in a performance billed as a "special appearance," chastises Susan for letting her "little Frankensteins" run amok underground, Mimic wouldn't dream of making her pay for her hubris.

Elsewhere, the picture is simply lacking in new ideas. Graphic designer Kyle Cooper should sue himself for ripping off his own title sequence from Se7en. Co-screenwriter John Sayles (Lone Star) should choose his projects a little more carefully. And I'll look forward to seeing del Toro's next movie. But those bugs are really, really great.