A.L.
Sounds like chiggers. They can live anywhere there are weeds/grass. They live on the branches of grass waiting for a host, then attack when you brush up against it. The spots usually will itch for a week. (sorry, yes it sucks) Try rubbing it with alcohol, then applying a hydrocortizone creme 2x day. It will stop itching faster, the more you apply the creme in my experience. Or good old calamine lotion (the pink kind) works great.