I have been bitten on the back of my knee by some kind of insect. I was wearing long pants tucked into my socks (I was picking blueberries). It is very red; about a 2 inch ring around the bite. The bite itself is blistered and itches and stings. This happened on Sunday and I just thought it was a chiggar bite until I looked at it today. Does anyone have an idea of what it could be? I took a picture but it is hard to tell anything about it.