I moved a stone plate in the garden in europe, that was stored vertically, leaning against another one. In the space between the two, I found some soil with small cavities filled with spiders.
Most of the spiders had a (what I think is a) larva attached to their backside. See the white sausage thing in the right half of the image. I noticed that there's what seems to be spider web on the right edge of the cavity.
Some of the spiders showed movement when lightly blowing air onto them. I took some of them out to get more detailed photos. The larva seems to have a white/translucent head attached to the spider body. The internals of the larva appear to be light brown through the translucent body. The larva has a thin white line at the sides of its body.
A while ago, I found other spiders in a comparable situation. Having learned that some wasps apparently catch spiders and paralyze them, to be eaten by their larvae, I did some search and found spider wasps
Is the above the work of a spider wasp? I had a look at bugguide - Family Pompilidae - Spider Wasps, but there are no images of their burrows shown.