At the Port of Los Angeles, a shipping container holds new weapons in man's battle against one of his oldest adversaries: Musca domestica—the housefly.

The mastermind behind this arsenal is Lorenzo Maggiore, an eighth-grade dropout turned artist who makes an unlikely merchant of death. The sinewy 51-year-old, who favors cargo shorts and wraparound sunglasses, is a surfer and yoga practitioner who speaks in a distinctly Southern California patois.

But when it comes to winged invaders, Mr. Maggiore is no peacenik: He is the creator of a plastic, pump-action shotgun that blasts pests with table salt—he calls it the Bug-a-Salt. While flies are his personal bugaboo, he says the weapon is lethal against mosquitoes, spiders and all sorts of irksome insects.