Comparison of development time and reproduction of typical and melanic Eurygaster integriceps (Heteroptera: Scutelleridae) under laboratory conditions

Among the sunn pest populations, melanic phenotype of Eurygaster integriceps Puton is a distinct colour morph. A set of experiments were performed to examine possible differences between typical and melanic phenotypes of E. integriceps using overwintered adults collected from Gharah-Aghaj mountains (southeast of Tehran). Melanics consisted only ۰.۳% of the total population. The laboratory conditions were: T = ۲۴ ± ۱ °C, RH = ۶۰-۷۰% and L: D = ۱۶: ۸ h. Incubation period and five nymphal instars were ۷.۲۴ ± ۰.۰۱, ۴.۱۴ ± ۰.۰۲, ۷.۹۷ ± ۰.۰۴, ۶.۶۳ ± ۰.۰۴, ۷.۲۱ ± ۰.۰۴ and ۱۱.۳۲ ± ۰.۰۷ days in melanics, and ۷.۱۹ ± ۰.۰۱, ۴.۱۴ ± ۰.۰۱, ۷.۸۳ ± ۰.۰۳, ۶.۱۹ ± ۰.۰۲, ۶.۸۸ ± ۰.۰۳ and ۱۰.۶۳ ± ۰.۰۴ days in typicals, respectively. Melanics with ۴۴.۱۳ ± ۰.۱۵ days had a longer developmental time than typicals with ۴۲.۳۳ ± ۰.۱۰ days. This difference was mainly related to the feeding instars. Durations of pre-oviposition period, oviposition period and post-oviposition period in both groups were not significantly different: ۱۰.۳ ± ۰.۸ days, ۳۴.۱ ± ۶.۴ days and ۵.۹ ± ۱.۹ days for melanics, and ۱۰.۲ ± ۰.۸ days, ۳۴.۹ ± ۶.۴ days and ۴.۰ ± ۱.۴ days for typicals, respectively. In general, reproductive table parameters showed an inferior performance of melanics compared to the typicals. There was no clear relationship between female body weight and total number of eggs in both groups. Stable population parameters (mean ± SE) of doubling time, Dt (days), mean generation time, T (days), net reproductive rate, Rо (female eggs/female), intrinsic rate of increase, rm (۱/time) and finite rate of increase, λ (per day), were ۱۳.۶۸ ± ۰.۶۸, ۶۰.۶۹ ± ۱.۷۱, ۲۰.۶۷ ± ۴.۰۹, ۰.۰۵۰۲ ± ۰.۰۰۲۵ and ۱.۰۵۱۵ ± ۰.۰۰۲۶ in melanics, respectively. The respective values for typicals were ۱۲.۷۹ ± ۰.۵۰, ۶۲.۶۰ ± ۲.۱۳, ۲۹.۱۱ ± ۵.۲۶, ۰.۰۵۴۱ ± ۰.۰۰۲۱ and ۱.۰۵۵۶ ± ۰.۰۰۲۲. None of these parameters were significantly different between two groups. Relatively inferior characteristics of melanics observed in this study need further experiments on their successive generations to elucidate reproductive performances of the group.