The green darner
Oct. 14—I've been wanting to feature this week's creature for years, but the need for further study always caused delays.
And while there is still much to learn about this fascinating species, the common green darner, I feel confident that now is a good time to feature it.
The green darner is a large dragonfly that is fairly abundant in the Ada area during the warm months of spring, summer and early fall. It is also one of the few species of dragonfly that migrates. However, the migration is complex and not fully understood.
Something occurred Oct. 5 that at least partially answered a couple of the few remaining questions I have concerning the green darner — how and when does it migrate?
I was returning home from a trip to the store when I saw a couple of dozen large dragonflies in a small area. It was evident that most of them were green darners. After a brief look around, it was clear that there were hundreds, then later, thousands flying around over a larger area.
While the massive swarm itself was slowly moving in a southerly direction, the individuals were just floating around in all directions, perhaps gathering food as they traveled.
But seeing this swarm of dragonflies also led to at least a couple of more questions. Were those just area dragonflies, or were they from farther north, perhaps much farther?
And if that's the case, since green darners also breed as far north as Canada, do they all migrate at the same time, or do area individuals see a migrant swarm traveling through and join the crowd?
But I am curious about something else as well.
A study a few years back showed that, similar to the monarch butterfly, the migration of green darners occurs over multiple generations.
The study concluded that the complex long-distance annual migrations are governed largely by temperature and involve at least three generations.
"In spring, the first generation makes a long-distance northbound movement (further than 400 miles) from southern to northern range limits, lays eggs and dies. A second generation emerges and returns south (further than 420 miles), where they lay eggs and die. Finally, a third resident generation emerges, reproducing locally and giving rise to the cohort that migrates north the following spring."
It is wise that the researchers said, "at least three generations," as I believe there may be more than three. Maybe.
Additionally, I've observed these insects laying eggs throughout the summer, and as late as early September. I can't imagine that those individuals that hatch in late summer or early fall could grow fast enough to migrate prior to winter.
So, while checking into it, I read where entomologists at the University of Minnesota, concerning green darners in that state specifically, noted that some green darners don't migrate at all and spend their entire lives in Minnesota.
"These dragonflies overwinter as naiads in frozen over ponds and emerge as adults the next spring once the weather warms up again," it read on the school's website.
So, are there some green darners that spend their lives in Oklahoma? Do the nymphs that emerge from those eggs laid in late summer spend the winter in the cold bodies of water in Oklahoma and emerge as adults in spring?
I am reaching out to experts with these questions, and I will be visiting some ponds over the winter in an attempt to find out. I will keep you advised.
Appearance
As mentioned previously, these dragonflies are large, growing to 3 inches in length and have wingspans which are a little over three inches.
Males have bright green thoraxes, and the abdominal segments are bright blue and black (photo). Females also have bright green thoraxes, but their abdominal segments very in color, from reddish brown to dark brown and bright green.
The entire abdomen is long and thin, like a darning needle, which is how it received its common name.
Habitat
Habitat includes marshy areas, ponds, lakes, etc.
Food
Green darners are exceptional hunters and hawk insect prey from the air. Insects taken include midges, mosquitoes, leafhoppers, beetles, flies, wasps and damselflies.
Nymphs prey on aquatic creatures, including the larvae of many insect species such as mosquitoes, along with small tadpoles and tiny fish.
Predators
Adults are preyed upon by many bird species, especially hawks and falcons, but also spiders, fish and frogs. I have spent many hours at small ponds watching the behavior of both the green darner and the American bullfrog. The bullfrogs made many attempts at catching the dragonflies but were only successful about 10% of the time. At least, that was the case while I was observing.
Range
Adult green darners are found year-round in places such as south Texas, Florida and Mexico, but their breeding range extends up into Canada during the summer months.
From about April into October, they can be found all over Oklahoma.
Odds and ends — Green darners are sometimes drawn to artificial lights at night. — The National Park Service reports that the green darner nymph has a spring-loaded labium (like a lower lip) which grabs prey and pulls it back into its mandibles. Because the rectum also contains the gills for "breathing," it can forcibly expel the water it is drawing in and out for breathing to launch a fast attack. — In the future, I will feature the green darner on my YouTube channel — https://www.youtube.com/channel/UCvw4ShsSHCjCt7Ypd2uGQzQ — and the video will include footage of the migration behavior that I witnessed.
