How can we make sure there are no more black widow spiders in house?

The best way to prevent spiders is to remove their food source. You can spray under your coach with rubbing alcohol and Tea tree oil. Of course, as soon as it gets wet, or the Tea Tree Oil wears off, the little buggers will be back.

I use 6-10 drops tea tree oil with 1/4 cup Rubbing Alcohol.

:)

Try this: http://www.wikihow.com/Get-Rid-of-Black-Widow-Spiders

Living in an area where black widows are very prevalent, I learned that the babies make sort of a parachute and float around on the wind. If conditions are right, they will be back as they like dark places.

I found keeping things clean and free of clutter worked well without chemicals. If I found a web - you can tell if it's a black widow as they have very messy webs, I'd kill her with a fly swatter as they want to stay and defend their web.

Defuse peppermint essential oil Put a few drops on cotton balls and put under furniture and in closets Defuse the oil daily for at least a week or more and then periodically