Ammophila urnaria acquiring caterpillar to stock egg burrow
The thread-waisted wasps are all known as “predatory” wasps, and are classified as “parasitoids”. Females dig a burrow with several chambers, and collect caterpillars to fill each chamber. They then lay an egg on the top caterpillar, and permanently seal the burrow. This is generally repeated several times, with between 2 and 13 burrows filled with caterpillars.
Thing is…the caterpillars aren’t dead. They have to manage to not become dessicated or decayed for the entire period between the laying of the egg and the pupation of the juvenile, a period sometimes longer than several weeks, during the summer. The female wasp stings the caterpillar around the abdomen with a nerve-destroying paralytic poison, and while paralyzed, the caterpillar body automatically utilizes the stored fat (normally used to metamorphose into a moth or butterfly) to stay alive and not rot. Occasionally the caterpillars have been found to die, or not be paralyzed the entire period prior to their becoming food, but the female wasp has an extremely efficacious venom. The caterpillars almost always remain in their chamber until they’re eaten alive by the juvenile.
After it pupates, the adult wasp is capable of digging out of the burrow from the inside.
Wasps, Social and Solitary. George Peckham and Elizabeth Peckham, 1905.