Beijing is crawling with a problem you cannot ignore. American white moth caterpillars are raining down from trees, blanketing sidewalks, and turning a simple walk into something close to a nightmare. The city's answer sounds like science fiction. Release hundreds of millions of parasitic wasps and let them do the work. Why has this year's infestation exploded and can this tiny-winged counterattack can actually work? On the show: Steve, Fei Fei & Yushan