What are the little red spiders all over my windowsills and walls?
Probably red spider mites they thrive in damp conditions usually on decaying wood. Even if you have PVC windows they may still be fitted to a wooden sub frame which under normal circumstances would not get wet so will remain dry and disease/pest free .The eggs hatch and they spread out spray insecticides will kill them but you need to find the underlying cause check all of the sealant around the windows especially externally.Ideally take the window out give everything a good clean and repair then replace and reseal. I don’t think they are harmful to living plants as they tend to eat dead wood but it is blood that makes the red spot which will stain a surprisingly big spot for something so small.
