ONE HOT SUMMER DAY in 1995 eight middle school children planning a simple study of wetland ecology began collecting leopard frogs from a small pond near Henderson, Minn.

• 1995年某个酷热的夏日，八个中学生计画了一个简单的湿地生态调查，准备在美国明尼苏达州亨德孙市附近的一个小池塘采集豹纹蛙。