Study on developmental threshold and thermal constant of Anthocoris nemoralis Fabricius, a predator of pear psylla

The adults and nymphs of Anthocoris nemoralis are efficient predators of eggs and nymphs of pear psylla, Psylla pyricola in pear orchards. The effect of temperature on different developmental stages of A. nemoralis was investigated under controlled conditions (65 ± 5% RH, 16L: 8D). A. nemoralis were fed by eggs and nymphs of pear psylla. The developmental threshold and thermal constant required for each stage and for egg-adult period were determined. The mean developmental time for egg to adult was 28.8, 19, 14 and 10.9 days for 20, 25, 30 and 35 ± 1 °C, respectively. Comparing developmental period of different stages showed that the fifth instar nymph with 28.23% and egg with 20.97%, had the greatest proportion of the total generation period Developmental threshold calculated from 8.04 (for fifth nymphal instar) to 13.89 (for egg stage). Lower developmental threshold and mean thermal constant for egg to adult were 11.8 °C and 259.92 degree-days, respectively.