The common green darner, Anax junius, is one of our largest dragonflies, measuring three inches long with a four-inch wingspread. It is strikingly colored, with a green thorax and a bright blue (male) or reddish (female) abdomen. As if that weren’t enough to set this dragonfly apart, it is also migratory. Common green darners migrate south from August through November, stopping over occasionally along the way to rest and refuel. Thanks to radio telemetry, we now know that over a two-month migration, these dragonflies, which weigh about one gram, can migrate over 400 miles. This photograph shows a common green darner perched on bottle gentian.