Processionary Caterpillar (bag nest)

Description:

This is one of the oddest spottings I've made in quite some time, and I really didn't know what I had found at the time other than it was some sort of nest. As it turns out, this is the nest of Ochrogaster lunifer, commonly known as the processionary caterpillar (which becomes the bag-shelter moth), and these caterpillars are famous for walking in single file head-to-tail processions. During the day the caterpillars shelter communally in a bag nest made of silk, frass (a type of insect excrement), shed skins, and other debris. Sometimes the nest is located on a shoot at the end of a branch, or sometimes high on the trunk. It can also be on the ground at the base of the food plant. The last two photos in this set show a second nest I found only a short distance from the first, but in slightly better condition. Both nests were found on a eucalypt species known as poplar box (Eucalyptus populnea), a common tree in the area. PS: The hairs from shed skins in such a nest can get blown around and spread over adjacent vegetation, which is of concern for humans and animals in the area. These hairs can actually cause horses to abort their foals. Here's an article about just that.... https://www.australiangeographic.com.au/...

Habitat:

Spotted along a sandy track at the Lake Broadwater Conservation Park.... https://parks.des.qld.gov.au/parks/lake-... This is a very flat area in a region known as the Darling Downs. Dalby is the nearest town. NB: Just a little over 12 months ago and this lake was completely dry due to the massive drought that Australia experienced. It's wonderful to see how the lake and surrounding bushland has recovered. Birdlife was abundant.

Notes:

I wasn't really too sure what I had found initially other than it was some sort of hollow nest. Parts of it was made from a silken web, but the external structure felt like stiff paper, and it had been woven around a tree branch. It also contained a fair amount of sand and grit, as did a second specimen I found a short time later (2nd last photo). Some of the leaves could be seen on the surface totally encased in this paper-like material. What had made this thing? Was it a spider, a wasp, a grub? I was dumbfounded! It was only by chance that I saw a post on a local community forum of a strange nest that someone had found in their backyard, and it was the same type of nest that I had found. It saved me a lot of time trying to ID the spotting!