What Are Those Dragonflies Swarming Around Milwaukee?

MILWAUKEE, WI — Groups of dragonflies in the hundreds have been spotted buzzing in the air around Milwaukee County in recent days, but what exactly are they and what are they doing here?

One such group of them was visible on Milwaukee's east side near Downer and Park Avenues on Tuesday. The individuals in the group seemed to have a greenish tint to them. Other swarms have been reported across Milwaukee elsewhere in recent days.

Several Patch readers noted the swarms seen recently in Cudahy, Caledonia and Lake Vista Park in Oak Creek. Others saw them near Grobschmidt Park in Greenfield (which is as far inland as 35th Street), or right in front of the Summerfest grounds.

It's not the first time swarms of dragonflies have captivated people across Milwaukee and beyond, but what are they?

One of the species might be green darners, or Anax junius, a migratory dragonfly that can be common at certain times of the year, according to Patrick Liesch, the director of the University of Wisconsin-Madison Insect Diagnostic Lab.

"They are one of our first dragonflies to appear in spring and a fresh batch of adults emerges in late summer, so we sometimes can encounter large numbers of sizable dragonflies," Liesch said in a statement to Patch. "They'll migrate to the southern US as well as parts of Mexico and the Caribbean where they spend the winter."

Milwaukee's Urban Ecology Center published a report on the green darner dragonfly in 2013. The species — growing up to the size of hummingbirds and boasting four gossamer wings — visits Wisconsin from April through September, the Ecology Center wrote.