Monday, February 18, 2013

Waterfalls and Wandering Gliders

During August of last year, I was doing some consulting work in southwestern Pennsylvania. In the time off I would visit state parks and forests. I was staying just West of the Central Appalacian Ecoregion, and Laurel Mountain was only 10 minutes away. This is a beautiful area of the state. The abundant mountain laurel reminded me so much of the Blue Ridge in South Carolina, where I did my Master's degree. 

One day I had the opportunity to visit Ohiopyle State Park.

The eponymous Ohiopyle Falls.
The town of Ohiopyle is situated on a large bend in the Youghiogheny River as it makes it's way Northwest to Pittsburgh, and gives it's name to both the surrounding state park and the 20 ft falls in the above photograph.

Ohiopyle Falls, looking from the West bank.
The Yough (say it like yawk) is calm enough upstream of the falls for swimming, but then there is a point of no return where the water tumbles over a sandstone cliff stretching the width of the river.

Looking downriver from the East bank of the Falls.
Downstream there are daily whitewater rafting tours. Brave kayakers are allowed to go over the falls on certain summer weekends, and there is an annual Over the Falls Race where many kayakers compete for best times.

Crayfish washed up at the edge
On the West side of the Falls is Ferncliff Natural Area, which includes a rocky, cycad fossil covered trail along the river. When the water is low enough, you can skip the trail for the exposed bedrock of the riverbank. I was able to rock jump out to the edge of the flow, where there were plenty of washed up signs of invertebrates, including crayfish and stonefly skins.

Ephemeral pool, ~3-4 feet across, ~1-2 inches deep
Here and there the rock formed shallow cavities which had filled with rainwater. Some of these had abundant mosquito larvae wiggling around, and some of them were strangely quiet. When I looked closer at these still pools I found the answer lurking in the sediment.

You can't see him, but he's there. The floating shed skin at the left end of the pool is a clue.
There are a couple dragonflies known for laying eggs in ephemeral pools, and after examining a larva under the microscope later, I was pretty sure which one. The mosquito larvae had all been eaten by a Pantala, a rainpool glider larva. Probably Pantala flavescens, also known as the wandering glider or globe skimmer. Wandering gliders are well known for their annual migrations accross continents and oceans worldwide, and equally well known for laying their eggs in any small pool, including artificial containers. I unfortunately didn't see any of the adults about; they have cheesy yellow colored abdomens, and paired with their effortless flight pattern they are pretty difficult to miss.

Dusky dancer (Argia translata) male, at the edge of Ohiopyle Falls.
I also spotted a damselfly perched on the edge of the falls. With the above photo I was able to confirm later that it was a male dusky dancer (Argia translata), a new one for my life list. What threw me off at first is the strange band of white near the tip of the abdomen. If you look close you can see it's pinching the abdomen like a damselfly elastrator (and if you don't know what that word means, don't look it up; this is your only warning). This ring of skin is probably left over from the last larval molt, which sometimes is incompletely shed. When the adult skin expanded and hardened, the leftover ring started pinching. This male is probably still reproduction ready, but it definitely doesn't look comfortable.

Cucumber Falls from above.
The big Falls isn't the only waterfall in the park. Off of the main channel, in a small tributary valley, is the smaller, more private, yet more spectacular Cucumber Falls.

Cucumber Falls from downchannel.

Walking up to Cucumber Falls puts me back in the rainforests of O'ahu. Albeit, the rocks are sandstone and shale, not basalt, but the feeling of overgrown lushness is the same. The ice cold stream drops off a natural overhang into a crystal clear pool with a school of black lined dace. And from there it disappears underground to reappear several hundred feet away, nearly at the Yough, seen through the trees at a distance. How many years have these dace been locked in, diverging under the selection of this small pool from their parents, either upstream or down?

Blacknosed dace (Rhinichthys obtusus?) in the splash pool at the base of Cucumber Falls.
And of course, any trip to a forest stream wouldn't be complete without the appearance of my spirit animal. 

An ebony jewelwing male, doing what it does best: glistening in the sunlight.
It seems I see Calopteryx maculata, the ebony jewelwing, no matter where I go in Eastern North America. They're common as can be, but still remain my favorite insect.

Acknowledgement: Much thanks to Stephanie Sanner-Fallon of Powdermill Nature Reserve for being my "tour guide" to the beauties of southwest Pennsylvania, especially Ohiopyle State Park.

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