The absolute efficiency of insect suction traps

SUMMARY The ways in which insect size, sampling rate and velocity, and wind speed affect the efficiency of suction traps were measured and an expression obtained to give total efficiency for most insects caught in most traps at most wind speeds. Tables converting log. catch per hour directly into log. density per 10 6 cu.ft. air, corrected for changes in volume of air sampled and for losses in efficiency under various working conditions, are given for 9, 12, 18, and 30 in. traps. In an appendix, a net is described that samples isokinetically in high winds and works efficiently as a whirligig trap in low winds.