The Newbery Medal-winning author of "Julie of the Wolves" goes south for this brief and gripping nonfiction portrait of the Amazon. It's a race against time, as Dr. Rivero and his young native guide save the rain forest from a lumber company. In the course of their search for a prize butterfly, they encounter sloths, army ants and birds -- all vividly described. A slim chapter book geared for children about age eight.  (FST08, $4.99)