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Alarm Orange

Orange spider with black diamond on the back – what is it?
Last night in our backyard there was a rather large spider orange with black diamond in the back. I looked at some websites and can not find a photo. We live in central Ohio, if any help. I wonder what is and whether to be alarmed. Thanks!
It sounds like a weaver, probably a marble Orb Weaver (Araneus marmoreus). You need not worry about them. They are not aggressive and would not do much damage if you were bitten, unless you were allergic to the sting. Here are some picture of them http://bugguide.net/node/view/2016/bgpage Hope that helps.