spider bites or mosquito bites, how do you tell the difference?

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The other morning my daughter woke up with about 7 bug bites on her leg. I don't know if they are mosquito bites or spider bites. She was outside the night before for a little while, but I had put some bug spray on her legs. She never complained about them and never scratched them, but they started to dry up and get scabby the next day. how do you tell the difference in bug bites?