I actually just came out of my crawlspace, quick break from framing. I keep mine fairly tidy and I will be adding electrical outlets and dricore. Getting it spray foamed eventually. Though I do have a "sub cralwspace" under my garage that is more dirty, and it used to look like this:
I cleared all of those (believe it or not I have a phobia of spider webs, spiders I could not care less, but spider webs, yes) and added lighting, then got it spray foamed a few years back, so it looks like this now:
My main crawlspace:
Unfortunately it gets spider webs too but not as bad as the first pic, even when I bought the house. The spray foam will probably solve that problem as it will seal all the cracks. I hardly get any under the garage now and the few that do end up there are probably spiders going from the first crawlspace.
Speaking of spiders, WTF is this? I'm pretty sure that's a spider web that got all crusty and dirty.
As for bug killer, I enjoy Cyonara 9.7. Get a pump sprayer and buy a bottle on ebay (seems to be the only place I can find it, it's probably illegal) and mix and spray.
Oh and on the subject of spiders, got a nice pic of one a few years back.
Check out those eyes! It's awesome. Clicky for bigger picture.