A modification of the Lincoln Index for estimating the population densities of mobile insects

Abstract. 1. To estimate populations of D.oleae in olive groves on Corfu by mark—recapture techniques, McPhail traps had to be used for sampling. 2. The prolonged sampling period (24 h) resulted in a differential loss of marked flies from the area and this biased the population estimates obtained from the standard Lincoln Index. 3. A modification was devised which enabled the rate of loss of marked flies to be calculated and incorporated into the Index as a correction factor. 4. Field comparisons indicated that the modified Index gave more accurate population estimates than the standard Lincoln Index and therefore it may be applicable to other situations when ‘instantaneous’ sampling of populations is not practicable.