Yesterday afternoon, a common green darner was zooming about our front yard. Easily identified by its large size and thick, green thorax, this dragonfly is common throughout most of North America and is known for its seasonal migrations, often in large swarms. On the other hand, some green darners do not migrate at all, wintering as aquatic larvae in ponds.
Autumn migrations, generally to Florida or Mexico, begin by September and spring migrants usually appear by April, often arriving before non-migrant darners emerge from the water. Of course, as with monarch butterflies and other migrant insects, those returning from the subtropics are the offspring of those that migrated southward in the fall.
Both the adult darners and their aquatic nymphs play an important role in controlling mosquito populations. For that and for their aerial displays, we humans are grateful.
