So what else do I do with my Pugio

[Carlton Bach]

I've been wracking my brain trying to figure out how a spider is used for shaving. Do they supposedly eat the hairs on your face?

OK, I think I'm getting a definite reputation as the 'Icky Guy', but...

My guess is it's spiderwebs, actually. Folk medicine uses cobwebs for treating minor wounds, the kind you could get while shaving. They staunch bleeding, hold the edges together and have antibacterial properties. OIl would serve a similar purpose, and reduce inflammation and skin irritation (as if Romans would need an excuse to add oil to anything)

As to shaving practice, I guess the advantage of depilation over scraping mioght have been that for quite some time afterwards, only a downy fuzz would regrow. That could simply bew burned away (as is recorded for Nero). Shaved hairs, on the other hand, would grow in their regular thickness and quickly get scratchy. And since Romans most likely did not shaver daily, the difference would be noticeable.