http://npic.orst.edu/factsheet.....degen.html

... Diatomaceous earth products are registered for use against bed bugs, cockroaches, crickets, fleas, ticks, spiders, and many other pests. ...

I buy it in 50 lb bags, OMRI listed and food grade, and I sell it by the pound to locals who don't need that much.   A few pounds should be plenty to do your entire garage and behind/under furniture in the house. 

Living in the middle of the desert, I've had a LOT of insect problems and I especially hate spiders.  I don't kill them outside, but it's MY house and since I DE'd everything in 2007 I've had very few insects inside except for little ants -- still battling those.

I don't usually use DE outside, haven't had many insect problems in the gardens and don't want to kill the beneficials.  I use a lot in my seed starting room with a dirt floor as I store a lot of "stuff" in it, sometimes the wind blows the door open and did I mention I hate spiders?

Many people also add DE to human and animal food that's stored long term to prevent insect infestation and some drink a little regularly, although I'm not sure that it does anything (see the studies referenced in the OSU DE fact sheet.)