Distracted by an unanticipated traffic transmission; a BE36 pilot fails to extend the landing gear prior to touchdown with predictable results.

Narrative

Upon reducing power over the numbers; I heard the gear warning horn. I began to apply power for a go-around; but saw the propeller stop. At this point; I continued the flare; focused on flying the airplane; landed the aircraft gear-up; and quickly exited the aircraft with two passengers. We proceeded a safe distance to the west into the runway grass and notified Emergency Personnel. This was the third of three takeoff and landings for night currency. The other two landings were uneventful. Upon turning base; I noted another aircraft nearing the vicinity. I made another radio call announcing turning base to be certain it was not a faster aircraft on final approach for our destination. This transmission interrupted my BCGUMP landing checklist. I believed that the gear was down and that I had three green lights until the prop stopped. In the future; this pilot-in-command should repeat the complete landing checklist if interrupted for any reason. If time does not allow for this; then a go-around should be undertaken.