Can they survive outside of nest/cocoon?
Sorry if some feel these are silly questions but I don't know much about larvae or the stages they go through, except that they eventually turn into an adult of the insect that laid the eggs. I have a mason bee house with a few grass carrying wasps nesting in it. There is another grass carrying wasp that has a nest in the split of a fence post located right by the bee house. I noticed it a couple of weeks ago when I was doing yard work because I saw pieces of grass sticking out of the split and I saw the adult wasp going in and out of that area. Today while I was raking up some grass clippings, I noticed a yellow looking worm/grub laying on the board below the split post. I walked over to get a closer look and saw another one laying right by it, along with some grass pieces and other material that looked like a nest. I scooped up the larvae and the material around it with a small garden shovel and upon doing that, I saw more larvae that had come out of their cocoons. I didn't know if they were suppose to be out of the cocoon this early or if it was the fall from the post that broke them open? Should I have put them back on the board where I found them laying or put them and the nesting material back inside the little cubby hole area where the nest was from the beginning? Are they suppose to be out of their cocoon this early and live like this until they're an adult wasp or are they suppose to stay inside cocoons until next year and then break out? Can they survive outside of the cocoon at this stage? Sorry for all the questions but I'm really interested in learning the answers. Thank you for doing what you do!
Interesting question, in deed, and good identification skills. Some insect larvae burrow into the ground to pupate, but Grass Carrier Wasps typically remain in their nest a few days to eat the food their mother brought them earlier, then pupate there or nearby. My guess is that these fell out of that split post or were removed by a curious animal or human. Since this question was passed around a little bit, I doubt these larvae are still larvae. Hopefully they found some food and pupated.
To directly answer your question, they are supposed to be crawling around as larvae for a few days, but they typically crawl around in the grass nest rather than on the ground. Their chances of survival outside the nest are slim, but could perhaps be greatly increased by restoring the nest in its original site - there is probably some hunting instinct that helps the larvae find the paralyzed food source.
Here is some more information about Grass Carrier Wasps: