The pilot stated that he was approaching his destination airport near dusk, and wanted to land before it was dark. The pilot forgot to lower the landing gear and the airplane touched down with the landing gear in the retracted position, which resulted in substantial damage to the fuselage skin, stringers, and wing attach fittings. The airplane was equipped with a landing gear configuration warning, which activated during landing; however, the pilot mistook it for a different warning indicator. The pilot further stated that he normally used a pre-landing checklist, but was distracted by the deteriorating weather conditions and did not utilize it. The pilot reported 3,079 hours of total flight experience, which included 50 hours in the same make and model as the accident airplane.