Creepy Crawlies!

I took a photo on 5th June of these when they were just eggs. Like shiny ball bearings on the outside of one of our windows.

Then they started to hatch and today they are wriggling! Masses of them!

What laid them, I wonder? It is an upper storey window so I would expect it to be a flying insect, a moth perhaps?

Anyway, because we don't have a regular window cleaner (I do it when I can) they have remained in place.

To be honest I find them unnerving and spooky.