Shell Hunting at the Wetlands

Ramshorn snail shell found
in the dry outlet wetlands

 The broad shallows at the outlet wetlands make a tempting target for exploration as January turns over into February. With much of the slumbering flora along the trail flattened by weather or equipment from the ongoing brush clearing restoration, and an afternoon silence signaling the absence of birds, this was as good a time as any to take the limited and seasonal opportunity to walk across the frozen mud and see what is normally hidden beneath water or greenery the rest of the year. 

Starting from the mowed path north of the apartments, there are several deer paths to choose from leading down through the brush to the wetlands (ducking under branches and squeezing my puffy coat between dogwoods flanking the path--I am neither as slender nor as agile as a deer, clearly). My chosen path landed me at the end of the outermost arcing berm, crunching through dry reeds and rushes that take advantage of the higher ground while the cells that hold stormwater on either side of the berm were flat mud, pocked with deer and other tracks and occasional bits of stone or rotting logs. 

I was on the lookout for a snail shell. The life that teems below the water's surface much of the year is a mystery, so finding evidence of mollusks while keeping my feet dry seemed like a nice adventure. It didn't take long to find: a delicate spiral, a little smaller than a quarter, resting on the frosty earth. A closer look revealed a tiny companion shell, less spiral and more conical. Both were delicate, absent the squishy residents who had previously called them home. 

Assorted small snail shells found near the outer berm of the dry wetlands..

A short distance away, another mollusk: this time half of a bivalve, but again quite small (dime sized, if we are sticking with coinage as a reference). A mussel? I recalled finding many quite large mussel shells during a cleanup at the Greenway's sister site nearby, Whispering Meadows Wetland Park. Do the Greenway's wetlands support a population of mussels?

A tiny mussel shell found in the outer arc of the outlet wetlands.

These fascinating invertebrates are important but often invisible parts of ecosystems, cleaning and filtering water as they feed. They rely on fish for part of their lifecycle: male mussels release sperm into the water, which find their way to females and fertilize her eggs. After the eggs develop into glochidia (larvae), they are released into the world--but they must find a fish to serve as a host for a few days or weeks, after which they will drop off and live the rest of their mussel-y lives at the bottom of a lake or stream. Some mussels can be very long-lived, thriving for many decades when conditions are right. Conditions including water quality, which we humans are doing a bang-up job of wrecking in and around our state, to the detriment of far more than mussels).

Walking slowly, looking closely. No luck encountering more bivalves within the outermost cell, I endeavored to visit the middle berm, not as easily accessible from land due to heavy thickets at either end. Crossing the low berm to reach the middle cell of the wetlands, again all was dry mud--but what was that shiny stone out there? And another....another! Big bivalves, everywhere! Or their remains, that is. How amazing that these critters can apparently thrive in our little wetlands! Perhaps the inner ponds maintain more reliable water levels than the outer arc, allowing more mussels to reach a larger size and greater numbers.

Dozens of shiny shells could be spotted in
the middle basin of the outlet wetlands.

Giant Floaters can be found throughout
the Mississippi River watershed.

A tentative ID from iNaturalist named these Giant Floaters (Pyganodon grandis), a "short-lived" (5-10 years) freshwater mussel that can reach up to 8 inches across. They are found in calm waters throughout the Mississippi River watershed, including ponds and reservoirs as well as slower-moving rivers and streams. Their evocative common name comes from the habit of deceased individuals floating to the water's surface as they decay. Their glochidia will latch on to a wide variety of fish, including lake sturgeon and largemouth bass--though the Greenway population's host fish are probably of a humbler stature such as minnows. 

When spring rains and snowmelt fill the wetlands again, we can imagine these big bivalves below the surface, silently filtering the water we sent their way. And maybe put a little effort into making their jobs easier by limiting the chemicals and other harmful runoff from our lawns and roads.

Sources/Additional Reading

• About Freshwater Mussels (Xerces Society)
• The Merit of Mussels (Xerces Society)
• Giant Floater (Missouri Department of Conservation)
• Pyganodon grandis (USGS)
• A Guide to the Freshwater Mussels of Nebraska (Steven C. Schainost/Nebraska Game and Parks Commission)

Giant Floater with a size 9 for comparison.

Live and let live?

 One of the few signs of insect life to be seen in the winter are egg cases, like the oothecae of mantids. 

The chunky, squared-off oothecae of Chinese mantids are particularly easy to spot long after leaves have fallen, affixed to twigs and small branches. Each can contain hundreds of eggs, though both cannibalism of siblings upon hatching as well as the general dangers any tiny insect faces in the world whittles down significantly the number who reach adulthood.

In recent years, more and more gardeners and native plant aficionados have been suggesting removing and destroying the crunchy-looking cases when encountered. Their contents are considered unwelcome non-natives with a nasty habit of mercilessly and indiscriminately devouring other insects, beneficial or not: bumble bees, butterflies, moths, and even the occasional unfortunate vertebrate, including hummingbirds, may become a meal. 

Our smaller native Carolina mantis may also suffer at the raptorial forelegs of its cousin; not only can the Chinese mantis — almost twice as big as the Carolina mantis — outcompete it for prey, the smaller mantis can also itself become prey for the larger. 

But the jury seems to be out on the extent of the harm caused by the Chinese mantis. It was introduced onto this continent more than a century ago, and has naturalized across much of the U.S., particularly in the eastern states without devastating effects thus far. Given the many other dangers little Carolina mantids and beneficial insects in general face from us, including habitat loss and pesticide use, we might consider leaving the oothecae and working to make our world more hospitable to all our insect friends. 

Chinese mantids and their egg cases have nothing to fear from me, at least. I still think they're neat.

Resources/Additional Reading

•  Missouri Department of Conservation: Chinese Mantis
• Challenging the Conventional Wisdom About Praying Mantids (NC Extension). Includes some great photos showing the inside of oothecae, with an anti-Chinese mantid perspective.
• Iowa State University Extension & Outreach: Praying Mantis
• Wisconsin Horticulture: Praying Mantids

Until we meet again....

With an unseasonably warm Saturday afternoon, I headed toward the Greenway in hopes of finding just a few more insects to visit with before the winter arrives in earnest. There have been a few frosty mornings already this year, but certainly some hardy arthropods would still be out and about? 

Of course those common home invaders can often be spotted on sun-warmed south-facing surfaces very late in the year: stink bugs and lady beetles, boxelder bugs. Winter midges and crane flies can also be spotted on warm days in cold months, as can tiny springtails. 

On this warm day, with the temperature reaching over 70 degrees, very few insects made an appearance. Regular katydid-like chirps could be heard from the grass, but I was unable to triangulate to a source. Nearly-invisible swarms of midges swirled in sunbeams. I paused at the alfalfa bales, where a couple weeks previous dozens of grasshoppers could be seen hopping and clinging to the sides of the bales. No chitinous wanderers, just a little junco watching warily from atop a bale. 

Nevertheless, it was a lovely, peaceful outing as even other humans had made themselves scarce. With quiet all around, even the smallest noise landed heavily on alert ears, and a glance in the direction of the small tick revealed a blade of grass moving just a little out of sync with its neighbors. 

Who's there?

Well hello friend! I thought I had seen the last of the neighborhood orthopterans until next year, but there was a hardy long-legged soul in the dry grass. Are you finding enough to eat, friend? There are still some green grasses along the trail. How did you weather the hard freezes a few weeks ago? How many others are still hanging on with you here in mid-November?

No answer was forthcoming, and the grasshopper had other business to attend to, despite my eagerness to spend the afternoon getting my fill of six-legged wildlife while I still can. But what a momentary treat.