What is this? Or, possibly, what are these on a post in the Potting Shed?

So far they could be – according to Google:

  • Bagworm egg cases
  • Bee moth cocoons
  • South African praying mantis eggs (not in North Wales surely?)

They are smallish – larger than a 1p coin, smaller than 2p – made of sawdust probably scraped off same pole; and rock hard (I hit one with a long metal pole and it didn’t make a dent). They remind me of limpets at the seaside!

Ideas please in case I have to protect my shed from wood boring insects, or ourselves from something bitey or stingy and very angry that I smacked it.

*University Challenge