What kind of bug bit my daughter?

My wife just noticed that my 4 year old has an extremely large, (2.5" diameter), raised red splotch on the back of her neck, just behind her earlobe. It does no itch and there is no pain. After close examination we discovered 3 more marks at her hairline of the back of her head. These are half the size of the first one. There is a small bite mark off center. No pus or open sores. Please help, we are wondering if she should be taken to the hospital or treat it at home?