1. Gents, a warning. Spiders are immune to some of the 'modern', safer insecticides- because they're not insects.
2.Gents, er...do NOT use mothballs to get rid of critters. A guy I know had a foine - the european stone marten, a mini-wolverine and not to be messed with - nesting in the roof of his cottage. He ordered his builder to throw a couple of boxes of mothballs around up there before finishing off a roof repair. Result: a]. Foine left home. b]. The house stinks permanently and powerfully of mothballs, but he can't remove them as he has no access into the roofspace.
Wood work but can't!