Naturespeak A naturalist's view of the world

August 24, 2012

The Exploding Grasshoppers of Lake Huron

Filed under: Uncategorized — wykes @ 7:21 pm

You’d think that a windy wet day on the Lake Huron shore might prove to be anything but productive but it was. The low expectations were met for most of the walk. It was nice to hear the waves crashing onto the isolated beach at Tawas Point and, thanks to the misty rains, to actually be isolated from public crowds.  But there wasn’t much wildlife moving about. There were no shorebirds, sand wasps, tiger beetles or any of the sorts I usually seek out in these dunelands. There were dozens of Ring-billed Gulls standing on the open beach beyond the “no admittance” sign (where the endangered Piping Plovers are nesting). All were facing into the wind and the group was being supported on exactly half the number of legs normally expected of such a flock because they were all balancing on one leg apiece. A wind-battered Buckeye was the only flier other than some swallows who matched the wind gust for gust.

Perhaps because of the lack of activity, I was forced to look sandward at the track evidence. There were, of course, numerous web-toed gull traces. The simple three-toed pattern of multiple small shorebirds imprinted the edge of the inter-dune ponds. They followed the edge of the shallow water for the most part. Singular holes, created by their probing beaks, pock-marked the sand.

In some stretches strange hieroglyphic letters and wiggles also marked extensive stretches of the wet sand (see above and here). There was some micro-mole type creature living within these sand lines – tiny openings at the end of some of the trials proved as much. The raised grains were drier than the darker background and were clearly outlined, but some of the tunnels obviously continued down into the wet sand. By the looks of things, there were thousands of these tunnels and thousands of tunnel makers.

In places where the shorebird and hieroglyphs met, a third type of marking evidenced where the birds were working these wiggle marks with systematic thrusts of an open bill. They were starting at one end and poking millimeter by millimeter down the line until – whatever it was – was found, escaped, or the hole turned out to be dry.  I opted to try the same tactic.

Taking my finger and collapsing the tiny ridges, I became a giant sandpiper on this day. Many of the tunnels yielded nothing except, well, collapsed patterns in the sand. A fascinating few of the tunnel investigations resulted in a tiny explosion near the terminal end. In a motion quicker than the eye could catch something would erupt out of the tunnel – spreading a small shower of sand grains and leaving an opening.  There was no obvious creature landing in the nearby sand, however, and that was intriguing. It was difficult to catch on camera, but I do have a short video clip to show the incredible details (o.k., the mildly interesting details).

These were tiny holes – only a few millimeters across – so the critter had to be hard to see just by matter of scale. After a series of trials, I finally trained my eye to spot the fleeing tunnel makers. Not only were they micro-sized but also cryptically colored to blend into the speckled sand (see below). Their surprising trajectory took them well beyond expected range to about 4 or 5 inches from their starting point.

It was impossible to nab any of these things in hand (I needed a beak but was without one at the time). Pushing the full capacity of my camera zoom, I did catch a few images (see above, below & here). If this were an ocean beach I’d be talking about “sand fleas” at this point but this was an inland sea beach. These things looked like grasshoppers but nothing about this scenario, except the jumping, smacked of grasshopper.

Let me say that I enjoyed the ignorance created by this whole affair and the identity challenges were both thrilling and frustrating but, for the purposes of this blog and your patience, I will now cut to the chase and leave out the details of the chase. These burrowing creatures were Pygmy Mole Grasshoppers. Appropriately enough, this species is known as the Minute Pygmy Mole Grasshopper.  How’s that for being called a speck on a fly’s rear-end!

Only 4 mm long, MPMGs are the smallest of the cricket and grasshopper group and perhaps the oddest. They inhabit moist sandy soil bordering streams and lakes throughout the eastern U.S. and feed upon the algae growing between the sand grains. Up close, getting beyond all those cryptic patterns, they have scoop-like front legs for digging, reduced wings (so they cannot fly), and huge jumping legs.  The end of each back leg has a set of flattened paddles – no doubt for sand walking or swimming (see my drawing below).

 

Being confined to soil dwelling as they are, it is surprising that Minute Pygmy G-hops have such well-developed jumping legs. Yes, they are grasshoppers but they do not hop in the grass. You do not see moles doing much jumping do you? The ability to burst through the roof of a tunnel and “fly” through the air is a great predatory evasion technique. They are world-class jumpers at that. For such a creature to jump 5 inches is equivalent to a human jumping nearly 14 feet. Consider that the world record standing long jumper is Arne Tvervaag who sailed 12.17 feet back in 1968. Arne did not accomplish his task by bursting through a sand roof as far as I know.

Finding a useless fact, like the one just quoted, is easy and instantaneous on Wikipedia. Finding Minute Pygmy Mole Grasshoppers is not an easy thing. According the rest (non-Wikipedic) information out there the best, and only time, to locate them is after a rain when their tunnels become evident. It was fortuitous that I was on that wet Michigan beach to discover something I had no idea existed.

3 Comments »

  1. Once again, you’ve shown us some of the magical creatures around us. Amazing. And your drawings are just amazing! Thanks again. Fascinating stuff.

    Comment by Karren Coplen — August 27, 2012 @ 8:06 am

  2. For a creature that small, 4mm, to jump 5 inches—–if the insect is as small as you indicate——the equivalent for a human being to jump would be not measured in feet, but in yards. 4 mm : 5 inches (126mm) :: 6 ft : 186 ft ……even though it is physically impossible it is still the ratio of that insect’s jump of more than 30X it’s body length.

    Comment by Robert Colgan — July 11, 2015 @ 9:53 am

  3. I was interested by your article and prompted to write you with a question that has long plagued me. I grew up on the shores of Lake Huron, eight miles north of Port Huron. My brothers and I would literally get up before breakfast and jump into the chilly lake. One thing that we were fascinated by was the occasional appearance of very smooth, crusty sand that erupted into tiny holes when we walked on it. As I remember all these years later, there was a little creaking sound as the sand gave beneath our feet. What is this phenomenon called? What caused it?

    Grazie,
    Jane Fowler Wyman

    Comment by Jane Fowler Wyman — October 11, 2016 @ 1:17 am

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