Enter the Dragon(fly)

 

Male Common Green Darner Patrolling the Pond Edge

The first dragonflies we normally see each year are the common green darners (Anax junius) pictured here. This is because the common green darner is one of several known migratory dragonfly species and these early season arrivals have flown north from somewhere down south long before any of the local dragonfly populations have emerged from overwintering as naiads or eggs (we'll get into "naiads" in a future post).  This year I saw the first common green darners at the wetland last Monday (3/22).  So far I have only seen males, as pictured. As with the frogs, the males have a vested interest in arriving early and staking out their territories so that they are ready to "welcome" any females that show up. In the case of the common green darners they patrol the edges of the pond checking likely spots that a female may choose for egg laying in hopes of finding a mate. I have not yet seen any females but they'll probably be along in the near future, and more photos will follow in another post.

Not a lot is known about dragonfly migration. Here in East Central Illinois there are probably six species known to be migratory in the sense of an annual north-south seasonal migration. Being strong flyers though, many other species may certainly disburse from where they emerge as adults to show up at other suitable bodies of water in the area.

The common green darner is the most thoroughly studied migratory dragonfly of North America, yet many questions remain unanswered.  One interesting aspect of this species is that not all of them migrate. The ones showing up this early in the year are certainly migratory because they are here too early for any of the local population to have matured. However, there are local populations of common green darners that have spent their whole lives here and will be emerging from the water in the next month or two. Genetic analysis has found no differences between common green darners that migrate and those that remain local, so it seems that the "decision" to migrate vs. breed locally may be determined by the timing of when an individual dragonfly reaches maturity.  As far as I know, the winter location of the fall migrants is not clearly known, but swarms can be seen feeding over prairies or fields or moving southward along lakeshores in the late summer and into the fall.

Dragonflies are a personal favorite of mine and I have some unanswered questions about the dragonflies that show up at the Homer Lake Wetland, so you can count on additional posts over the next months on the lives of the dragonflies. You have been warned.

Male Common Green Darner, 3/31/21 -- note the orientation of the wing pointed down. The ability to "flap," flex and bend each of the four wings individually and independently is unique to dragonflies and damselflies.
(Click photo to view larger.)

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