My mother swears up and down by boric acid. Said she killed every roach in our apartment building in Texas using it. She took the light switch and electrical covers off in every room and dumped it into the wall (turn the electricity off before doing this so you don't accidently shock yourself). Boric acid is not a dangerous poison like most, although you should try to keep pets and babies out of it. I was a baby at the time, thus why my mother put it in the walls. But then, that's where roaches live.
I have heard that fuller's earth is also effective, although I think that's supposed to be used outside, like around the foundation (about as posionous for pets and babies as the boric acid). That's good for all sorts of bugs that may try to get into your house.
Also, you can apply instant grits to ant hills; ants eat the grits, swell up when they get water, and then die. If they are coming into your house and you can't find the hill, you can use ammonia (Windex, etc.) to spray them. The ammonia will not only kill the ants, but it completely overpowers the scent trail that they use as a road. They will not come back in through a hole that's been sprayed with ammonia.
You can also use ammonia to kill flying things. I get out my bottle of Windex when we get wasps in the house and I squirt them when they are flying around or have lit somewhere I can't reach. They will get confused and will either fall to the floor or will lit somewhere low where I can finish them off with the flyswatter (they are very slow after this). The ammonia will eventually kill them by itself, but I prefer to finish them off and get them out of the house.
Use a professional exterminator if you have brown recluses, though. I don't know of anything you can do yourself that will kill them as well as the exterminator's poison. We had them bad in our house a couple of years ago, but with three months of exterminating, then quarterly extermination, we've got them beat back out of the house (still bad in the barn, though).
