Based on boundary layer meteorology , the tempora-l and spatial distribution and the behaviour of migrating insects were reviewed, and a concept of 'PBL-top phenomena' was pre sented. The surface inversion .subsidence inversion and low level jet near the top of PBL pro vide an optimum wind and temperature field lor the airborne populations, where there are maximum wind speed and temperature. The insects actively take oif,climb ,and then layering in the top of'PBL. They also orient to a special azimuth to mo...