INFLUENCE OF TEMPERATURE ON THE DEVELOPMENTAL RATE AND REPRODUCTION OF THE ENGLISH GRAIN APH-ID, SITOBION avenae (FABRICIUS) (HOMOPTERA: APHIDI-DAE).

A laboratory investigation was conducted to study the effect of constant tempera-ture on some biological aspects of english grain aphid, Sitobion avenae (Fabricius). The present work was carried out in electrical incubators provided with photoperiod of 16 : 8 (L : D) and 55 – 60% R.H. Data revealed that the english grain aphid passed through four instars to reach maturity. The duration period of the nymphal stage was 19.0, 13.98, 11.96, 8.51 and 7.5 days at 12, 15, 18, 21, 24 °C, respectively. Developmental threshold of this stage is found to be 4.2 °C. The thermal units re-quired for complete one generation was 148 day – degrees. Life table parameters were as following : The reproduction rate (Ro) were 18.75, 30.72, 36.53, 44.21 and 32.42; mean generation time (GT) were 26.16, 21.23, 17.39, 11.92 and 9.86 days; population doubling time (DT) of the english aphid were 6.19, 4.29, 3.35, 2.18 and 1.96; intrinsic rate of increase (rm) were 0.1121, 0.1613, 0.2069, 0.3178 and 0.3528 and finite rate of increase (λ) were 1.119, 1.175, 1.229, 1.374 and 1.423 at 12, 15, 18, 21 and 24 °C, respectively. The results indicated clearly that the favourable range temperature for development and multiplication the english grain aphid be-tween 18 and 24°C.