The small tower or "chimney" in the photo is made up of 1mm pellets of rounded mud. There were a few such towers on a bush track at Sulky. The height of the tallest was 35 millimetres.
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The inside diameter was the width of a pencil.
READ LAST WEEK'S NATURE NOTES HERE: Why this magpie was sunbathing in Ballarat
These were built by a mason wasp, a slender black species about 15 mm long.
The female wasp has dug a nest in the hard, dry clay track. She has constructed this chimney like structure from the dug clay, having previously wetted the digging site with water. The purpose of the tower is unknown.
The towers are not strong, being readily broken by passing kangaroos and wallabies.
Some mud-building wasps make large oval nests, which they smooth over as they construct.
Others make rougher, more slender nests that are often found on the outside of houses or in sheds. These have numerous segments within, one for each insect or spider that has been paralysed by the wasp as food for her grubs.
Many years ago, this column showed a similar tower that was mistakenly stated to have been made by a yabbie of some sort. It was a wasp tower like the one shown today.
- Got a question for Roger? Use the form below, or send your question to rthomas@vic.australis.com.au, or send to Roger Thomas at The Courier, PO Box 21, Ballarat, 3353.