Skin reactions are pretty personal. Are those bed bug bites or an allergic reaction to new laundry detergent? A poison ivy rash can look exactly like a mosquito bite. The only way to tell what bit you is to see it biting you. You just can't tell by the reaction itself.
Some of these critters don't technically bite, but people say they do. So here is a list of piercing, pinching, stinging, sucking, and, yes, biting pests.