If you go outside after dusk this time of year, in a place where there is a bit of vegetation, even better somewhere undeveloped and dark, you may get to see the greenish yellow flashes of the firefly. How can an insect make light? Why do they, and what do the flashes mean? Living Lab host Heather Goldstone gets the answers i n this interview with Sara Lewis, Professor of Evolutionary and Behavioral Ecology at Tufts University , who's written a new book entitled Silent Sparks: The Wondrous World