抄録
As the first stage of the reason elucidation that Swarming which was the collective motion of bacteria was performed, acquired velocity before bacteria increasing in PIV, and measured correlation of the velocity. As a result of the measurement, correlation appeared an angle between the velocity and the distance of lattice point between 20 when it became the collective motion. In addition, measured about the standard deviation (S.D.) of the angle between the velocity. As a result of measurement, knew start time for Swarming from a decrease in S.D..
