Though the poster for Jennifer's Body lacks the fangs of it's twin, the blood and ruby red lipstick still evoke fears of the vagina dentata with an image that is simultaneously revolting and arousing.
Horror has long been considered a body genre, as Barbara Creed explores in her book The Monstrous Feminine: Film Feminism and Psychoanalysis (the cover of which also resembles the above posters), with films featuring the abject feminine body as the source of fear (The Exorcist, Dog Soldiers). That said, Jennifer's Body seems like the perfect title for a film that seeks to explore fears of powerful and destructive female sexuality (Jennifer does say she swings both ways).
Looking at the trailer, Amanda Seyfried of Mamma Mia! plays Jennifer's reluctant and sexually inexperienced sidekick, Needy Lesnicky. Her name is enough to conjure up images of a shy, bespeckled outcast, the veritable final girl of the film.
The dynamic between Jennifer and Needy resembles the relationship of the Fitzgerald sisters in Ginger Snaps (2000). Ginger becomes sexually active after being bitten by a werewolf, compared to her plain sister Brigette who has an intense fear of the "human circumcised dick." Needy's fear of intercourse, displayed in her screaming during sex with Chip (to which he responds "Am I too big?") and fear of being murdered/ravished by Jennifer, plays foil to Jennifer's insatiable lust for blood and sex.
But Jennifer's motive for the brutal murders she commits is provided by the adolescent boys who objectify her sexually. When Needy gasps "You're killing people," Jennifer coolly responds "No. I'm killing boys," as if to suggest that in turning her into a sexual object for their own gratification, those "boys" aren't even human. They want inside her body, so she turns the tables and devours them instead, putting them on the receiving end of the sexual encounter.
Male impotence against the power of female sexuality is underscored by Chip's conversation with his mom in the final seconds of the trailer. Chip's mom offers him pepper spray for protection (much like a mother might give to her daughter) but he replies "I can take care of myself. I've been using the BowFlex." The following shot is of him being dragged into a murky pool by the ruthless Jennifer. So much for the Bowflex.