The green darners (genus Anax) are large, robust, strong-flying and often migratory. Two species are known to occur in Wisconsin, one is very common, the other rare and possibly just an accidental stray. Both are easy to identify, even in flight.
This large, strong-flying darner is readily distinguished by a solid green thorax, largely blue abdomen (males) or reddish-brown abdomen (females), and a distinctive "bulls-eye" pattern on the forehead of both genders that is easily visible from above. All ages have a dark stripe on top of the abdomen that widens towards the tip. Comet darner is most similar, but the male of that species has a bright red abdomen. Though females of the two species are somewhat similarly colored, separate them by the presence of "bulls-eye" mark on forehead and dark stripe on top of the abdomen of common green darner (female comet darner lacks both marks). A useful identification clue sometimes seen even at a distance – pairs usually oviposit in tandem which is a unique behavior among North American darners.
Widespread and common from southern Canada to Mexico, this species is found at a variety of still and slow-flowing waters, including marshes, small ponds (may be semi-permanent), lakes, sheltered bays, and slow streams. Preferred habitats often lack centrarchid fishes (primarily sunfishes [genus Lepomis] and black basses [genus Micropterus]).
This species is one of our few truly migratory dragonflies with a long and early flight period, but with a resident (non-migratory) component of the population as well. Spring migrants arrive from the south in April. Reproduction occurs upon arrival, nymph growth rates are typically fast, and new adults emerge in late summer. Large numbers of young adults are often seen migrating south through Wisconsin in late August and September.