I love using nature in art making activities. The key to making bugs out of rocks and found nature is using artist's heavy gel medium as the glue. This is like a thick paste and will join the pieces together so the children can do all the work themselves.
Making a Rock Bug and its Habitat from Fairy Dust Teaching on Vimeo.
I put out a tray of things for the children to use in their bug making.
To make the bug's habitat, I purchased small paper bags at Michael's. I prepared the bags by cutting an opening. I had the children glue the bag to a small paper plate. Then they glued on different materials to create a habitat.
This is a tray of found materials (from my morning walk) to use in habitat making.