What are the bare spots in my lawn?

I live in Cincinnati Ohio, and my backyard, in the sunny portion of it, has bare spots that have been gradually growing over the last years. One of them is about 10 by 20 feet. Areas away from the spots are growing well. I suspect that some sort of insects are contributing to the spots because they seem to get bigger every year. In particular the spots are mostly bare with small clumps of grass interspersed in between the bare ground. Can someone tell me what I have and how to fix it. Thanks,
JD
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On Thu, 24 Apr 2008 04:10:48 -0700 (PDT), JD

Can't say for sure, but I suspect grubs are eating the roots. Dig up a square foot area 4" deep at the edge and sift through the sod. Your selected area should be half bare ground, half grass. It is okay to have one grub per square foot, but any more than that you have a lawn problem. There are a few effective methods to eradicate/control grubs. Bare sunny areas in the lawn can create another problem: crab grass. Lawn repair takes patience, especially when neglected for several years.
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