What are these two strange itchy marks?

Last week, I noticed an itchy spot on my back and could feel a slightly raised bump.  Even a week into this, I still feel it's a bit itchy and the bump is still there.  I could say it looks a bit like a small mosquito bite...

Could it have been a spider bite of some kind?  I did notice a few rather nasty looking spiders wonder into my desktop workstation a week ago and so I can't but wonder if it's related.

any other ideas, suggestions, cures?

[85dave]

I should note the title is a bit wrong and it's just one mark upon reviewing the photo i snapped a bit closer.