Redheaded flea beetle adult. Photo by Lewis Veith.
I had to do a little digging in the literature (and got some help from a fellow entomologist named Brian McCornack at Kansas State University) and found out it was called the redheaded flea beetle. Like most flea beetle adults, they jump away if disturbed. But they can be captured in a sweep net if you move fast enough in soybean.
Adults are about 1/4-inch long with black forewings, large jumping hind legs and a red head. They are the same shape as bean leaf beetles, but overall smaller in size. If you happen to see this insect in soybean (or any where else), I would be interested in hearing from you!