Hole in my garden, about 2cm across, with a small pile of dirt that has been dug out. Probably not a coincidence that it is beside the weeping hose, as the soil here would be easier to dig. I've been using the weeping hose to water the garden once a week or so.
Insect? Arachnid? Crustacean? I don't know, but I wasn't going to stick my finger into the hole!
Found the answer in March. See this post.