Kate Taylor and husband Clint live on and manage our Bon Bon Reserve (SA). She recently noticed these creepy and dangerous sacks – home to Processionary Catepillars (Ochrogaster lunifer).
By day the caterpillars hide communally in these nests made of silk, insect poo, old skins and other debris.
This stuff can cause bad skin rashes and even touching the caterpillars themselves can cause a bad reaction.
Feeding nocturnally, they leave each evening and at dawn return to their nest. You may see them in their weird processions during the day if they totally defoliate their food tree (often wattles or Beefwood) and are on the look out for another one or when they're ready to pupate (which they do away from their food tree in a silk cocoon in the ground).
As their name suggests they walk in long processions. Each caterpillar keeping in contact with the one in front. When they walk they leave a trail of silk, which helps them navigate back.
When a caterpillar of the species encounters such a trail it will follow it. There can be 100 or more caterpillars in a head-to-tail procession, kept together by contacting the tail hairs of the caterpillar in front.