Re: Poison Ivy?
Bugs bite you all over, and don't last a week.
...
Not always. From some online chigger information:
"On its host, the chigger usually moves about until it reaches a place where it is somewhat confined, such as around ankles, under socks, or behind knees. when people sit on chigger-infested ground, frequently they may get severe chigger bites around the waistline or in the crotch area, especially under belts and elastic bands of underwear. Sometimes chiggers may move to the upper torso and attack the armpits. Chiggers become active in June, but outdoor activities and warm days around the Fourth of July result in increased complaints about chiggers."
That being said, it does look more like a rash rather than a group of small welts caused by chiggers. Maybe a reaction to a chemical put on the grass??