Tuesday, June 2, 2015

Big Bugs!

Near the Eyre Peninsula are some wonderful sand dunes and I came across these strange "fossilised" shapes in the sand. Turning them over gave no indication of what they were, or why there were there. Was it something to do with lightning strikes fusing the sand in the extreme heat? They weren't fossilised wood, as they were too uniform and tree roots and branches are anything but uniform! In my mind they look like Dead Man's Fingers, gnarled and arthritic.

I posted a picture on FB and G+ and had some interesting suggestions, but nothing seemed to fit with the location, shape and sheer number of them. They only seemed to come in two shapes, finger-like ones, some hollow, some solid; and egg shaped ones, some incredibly fragile, others thicker and filled with sand. When tapped gently together, they make a flat, glass-like sound.

They're clearly different to the formations below, which look like sand, blown into random formations by salt laden winds. These are strange, surreal shapes, some like skinny mushrooms on top of spindly trunks, others curled and twisted into tortured shapes.
And different again to tree roots or branches. These are long, misshapen, hollow and generally near the tree line or vegetation. There's lots of variability in both length and shape.

My mystery objects were spread over a wide area, and didn't appear to be specifically related to the vegetation at all. They seemed to be mostly in large (really large!) bowl like depressions and I wondered (not knowing anything about these things at all) if it could have something to do with salt laden winds somehow blowing the sand up the incline and it rolling back making the shapes. Unlikely and weird, but nature can be like that sometimes!

Frustrated by conflicting suggestions, I wondered if the Museum of Victoria might have someone there who could confidently solve the puzzle. One email, and a couple of hours later I had this response from Simon at the Discovery Centre:
We think these are the remains of cocoons of a native weevil, Leptopius duponti. These calcified cocoons are not always regarded as ‘fossils’ in the strictest sense, but nonetheless may be quite old depending on their original locality – for example they are quite common in the sand dunes of the West Coast of Eyre Peninsula in South Australia. Some examples of these calcified cocoons have proved to be made of sand or gravel cemented together, and sometimes of limestone. The distinction of whether they are fossils or not depends on the chemistry of the material that holds the cocoons together.
In 1925 it was reported by A. M. Lea in the Records of the South Australian Museum (3; 35-6) that these sands contained the calcified pupal cases of insects, more specifically weevils of the genus Leptopius (see attached for this article and illustrations). As this type of weevil is still alive today, commonly called “Wattle Pig”, we now know the adult female Leptopius sp. feeds on the foliage of acacia trees and lays her eggs on the leaves. When the larvae hatch, they are thought to burrow underground to feed on roots, and when ready to pupate they make a chamber in the soil instead of a true cocoon which is cemented by a secretion from the larvae (rather than a webbing, in the case of other taxa). The emergent adult then climbs the trees to feed, and the empty cases are left to weather underground and can become mineralised. Some of these cocoons from the Eyre Peninsula are estimated to be up to 40,000 years old.
Hooray for Simon at the Discovery Centre!!

And as someone commented, that's one large weevil, and from the point of view of the acacia trees, it could well be an evil weevil!

Now to find out what these are! About 10cm long, found at Mt Remarkable.

And then there's this critter lurking in the toilets at Mt Remarkable, he looks particularly unfriendly ... I hate the thought of finding him under the toilet seat! That's a standard house brick (3"or 75mm) he's sauntering over and looked like something I'd expect to see in the tropics.
And last, but by no means least, a moth the size of a small bird at Mt Ive. It was quivering and difficult to photograph with a phone, but you can get a sense of the size (again on a standard house brick). He and the centipede are about the same length, but the wings on the moth were massive!
Isn't nature awesome!



Drhoz said...

The moth and the discarded pupal cases are related - Hepialid rain moths :)

Sue T said...

Thankyou! drhoz. It's great to get some information so long after I posted this. Cheers, Sue.