The flight habits of the alfalfa seed chalcid, Bruchophagus roddi Guss., were studied using natural field populations and reared insects which were radioactively marked. A minimum temperature of 70°F and a minimum light intensity of 0.2 Langley was found necessary for sustained flight. In a favorable host area, the chalcids dispersed only a few hundred yards within a few days. The movement of chalcids in a breeze less than about 5 mph was both upwind and downwind. In stronger winds, movement was predominantly downwind. The data obtained suggest that when a host area dries or otherwise becomes a nonhost area, the chalcids fly upwards where they encounter the stronger winds and rapidly leave the area. Marked chalcids were recovered 4,100 feet downwind of a release point; others were observed to survive 16 days in the field.
