PORTLAND, OREGON—Venus flytraps have a well-known way of dispatching their victims: They snare inquisitive insects that brush up against trigger hairs in their fly-trapping pods (above). But now, physicists have discovered that the triggering process may involve the release of a cascade of exotic chemicals similar to the whiff of ozone that tingles your nose after a lightning bolt. To study this process, scientists used an electrical generator to ionize air into a “cold plasma,” which they then gently blew toward a flytrap in their lab. Normally, the flytrap’s closure is caused by an electrical signal created when two or...