Demographic Parameters of Two Populations of Trissolcus grandis (Thomson) (Hymenoptera: Scelionidae) at Five Constant Temperatures

Abstract

Trissolcus grandis (Thomson) (Hymenoptera: Scelionidae) is the most important egg parasitoid of the common sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) in Iran. Demographic characteristics may be used for preliminary screening of parasitoid species or populations as well as for predicting their efficiency under different physical conditions in the field. In this study, the demography of two northwestern populations of T. grandis was studied under five constant temperatures including 20, 23, 26, 29, and 32±1°C, at 50±5% RH and 16:8 h (L: D) photoperiod. The two populations responded differently to the temperatures, thus, many life history parameters were significantly affected not only by temperature itself but also in interaction with population. The highest value of intrinsic rate of increase for the Marand population was 0.344±0.057 females/female/day that occurred at 26°C. The same rate for the Tabriz population increased regularly with temperature increase and the maximum value (0.368±0.063) was obtained at 29°C. Further increase in temperature led to a negligible change in the value of this parameter. As a whole, the Marand population seemed to be adapted to cooler conditions compared to the Tabriz population Keywords: Egg parasitoid, Eurygaster integriceps, Intrinsic rate of increase, Life history