On December 17, 2003, about 1650 eastern standard time, a Waco 4MF-5, N64JE, registered to TN Delaware Air Corp., and operated by a private individual, as a Title 14 CFR Part 91 personal flight, ground looped during landing rollout on runway 25, at Marathon Airport, Marathon, Florida. Visual meteorological conditions prevailed and the commercial rated pilot reported no injuries. The airplane sustained substantial damage. The flight originated from Marathon, the same day, at about 1620. The pilot stated he departed from Marathon Airport at about 1620, and performed two full-stop landings on runway 25. The winds were from the west-northwest at 15-20 knots. During the third landing while on landing roll, at about 10 mph, the tail wheel started to shimmy and the airplane began to turn into the wind. The airplane then continued around with the left wing tip contacting the runway. The airplane incurred damage to the left aileron and left outboard wing rib. The pilot inspected the airplane and then taxied back to the parking area. The pilot reported he had no mechanical difficulties with the airplane.