Brown indents - possible spider

[jhadley]

Excuse my ignorance - I bought an Euphorbia Acruensis to brighten up my living room. Within a day, I noticed some brown indents on my otherwise healthy cactus (see photo). I didn't know what they were but I noticed that his pot was too small and the soil was dry. I re-potted him (surprisingly difficult!), added soil and made sure the soil stayed moist since then.

He still occasionally gets these brown indents and yesterday, I saw what looked like a piece of cobweb near them. I didn't think there was a spider in my living room but of course, it's not beyond the realm of doubt. I have 2 questions:

1. Does this look like a spider's doing?
2. What is the best way of dealing with it? Spider repellant on the outside of the pot maybe? At the moment, the pot is on a table.

[teo]

Possibly spider mites (not spiders) - but in my experience they rarely attack Euphorbias.

[HP22B]

Looks more like mechanical damage. Have a cat?

[jhadley]

I don't have any pets