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Dragonflies and Plants

Travel plans prevent a Friday fieldtrip this week, so a preemptive strike now a day early.    This week there are dragonflies in the skies, lots of them.    Halloween Pennants. So enchanting, so acrobatic,  and so molested by all our water pollution and its consequences, but no soapbox here.  Keep it fun.

Halloween Pennant Dragonfly 1 (1)

Halloween Pennant.  All still photos today by John Bradford.

Today the mission is to connect dragonflies with plants.   The first obvious thought then is, “do they pollinate flowers?”   Not an unnatural notion  given all the marsh plants with flowers on top, just where dragonflies perch.   Although dragonflies are not often credited with pollination benefits,  the late Dr. Peter Yeo,  go-to botanist for pollination,  suspected dragonflies as likely pollinators for some Xyris.   I’d be an easy sell on that.

Xyris caroliniana 1

Xyris

Even though dragonflies probably don’t deliver much pollen, they will not be denied a role in flower biology.   As anti-pollinators!  Dragonflies are wicked predators while as larvae in the water and as adult insect-gobbling attack copters.    A couple studies over the years have shown dragonflies to reduce pollinator populations sometimes enough to matter.    Not really a “bad” thing, merely a hand in the balance of nature.

Golden-winged Skimmer Dradonfly

A third impact for dragonflies on plants is more subtle.    The big lugs move nutrients from aquatic ecosystems outward to terrestrial systems.  This might add up to significance, given the abundances, sizes, and appetites of dragonflies,  transferring nutrients from their aquatic cradle to wherever they perish, perhaps during massive migrations, or possibly as a bird snack, and along the way, devouring and spreading the remains of insect prey.    Dragonflies can live multiple months.

Blue-eyed Darner Dragonfly 1

Humans can benefit from, even use, the insecto-destruction powers of dragonflies.  They are valued pest control agents in rice paddies, and have been contracted to help control Zeka-bearing mosquitoes. A small number of dragonfly larvae can remove a lot of mosquito larvae from their watery beginnings.

For a wacky interspecific collusion, consider related damselflies whose submarine larva positions itself to promote photosynthesis by algae (Euglenoids) within the flesh of the larva, the larva benefiting from the oxygen the algae emit.

Spreadwing Damselfly

Dragonflies are territorial, although I think you’d have to be one to understand their social signals during short missions darting around interspersed with restful moments perching, then sometimes visibly munching their victims.   As a dragonfly watcher, I have stumbled into a mystery:   leg-waving, encountered repeatedly.     Why a perched dragonfly might wave a leg could be anything from a social signal (my guess) to itchy toes.   If anybody really knows why, the truth has escaped me…and I’ve tried to find out.  Watch the wave in the video below, and make a guess.

FLIT HERE to see dragonfly action!

 

 
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Posted by on May 11, 2017 in Dragonflies, Uncategorized

 
 
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