What bug bites cause circular pattern?

Many: Papular urticaria, as it is called, is what is typically seen from bites by mosquitos, spiders, etc. Usually reactions to the saliva trigger itching, redness and a small bump that resolves in a couple days. Bigger reactions (redness, tenderness), can mean infection; circular rings around the bite may also raise concerns of tick bites leading to Lyme disease; early treatment is very effective.