At Duck End Nature Reserve this afternoon (1st July) an Ammophila sabulosa found this caterpillar and dragged it back to her burrow. She then spent some time enlarging the burrow before dragging the caterpillar in.
During the enlargement process she briefly wielded this pebble seemingly like an hammer bashing the opening before discarding it and digging again with her feet and jaws...
Once the caterpillar was housed the hole was filled in, using her head as a vibrating ram - I could hear her buzzing as she packed the material hard. Small pebbles were finally arranged over the surface.
Pictures by Keith Balmer