Marsh Survey Update


by Carl Strang

The marshes at Mayslake Forest Preserve continue to warm into the season. Less than a month ago, in late March, there still were mornings when skim ice formed around the edges.

The ice was thin and crunchy when I waded out to check amphibian traps.
In addition, there was plenty of humidity in the air for producing ice crystals.

One of the more remarkable events at the stream corridor marsh was the prolonged visit by a pair of bufflehead ducks.

Here the female takes a break from swimming.

The buffleheads stayed for more than two weeks, finding plenty of food while they waited for the weather to moderate.

Plants have begun to grow. Here a muskrat gnawed off some tips for its dinner.

The rodent’s incisors clip the leaves cleanly.

Over in the parking lot marsh, the traps have been producing some bullfrog tadpoles.

These have been around 3 inches long.

Last week in the stream corridor marsh I caught what appeared to be a second species of large predaceous diving beetle.

I was alerted by the filled zone of yellow at the back tips of the elytra.

Several characters pointed to Dytiscus hybridus. It was lucky to be alive. Overnight rain had elevated the marsh so that the trap was completely under water and the beetle could not reach the surface for fresh air.

It floated at the surface for a long time after I released it. The cold water, and some diffusion of oxygen into the bubble held beneath the wings, apparently allowed the insect to survive.

Now I have to look at all these beetles more closely. Later I caught one that seemed in some ways to be between the two known species.

For instance, there were thin yellow lines at both front and back edges of the pronotum.

Underneath, though, the brown color with some black placed it in the more common species, Dytiscus verticalis.

Now I’ll need to look at tops and bottoms of all of these I catch.

I thought for a time that I had caught a second crayfish species. Unlike the white river crayfish I caught earlier, this one did not have a dominant burgundy color.

It was mainly greenish.

It proved to be the same species, though, when I carefully went through all the physical features. Little experiences like this give one a concrete sense of the variability within species, which also is an aspect of biodiversity in the broad sense.


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