Individual Variation in Progeny Diapause Induction in Trichogramma telengai Sor. Females (Hymenoptera, Trichogrammatidae)

Abstract

Individual variations in the proportion of diapausing progeny of Trichogramma telengai Sor. (Hymenoptera, Trichogrammatidae) females of the parthenogenetic strain were investigated under laboratory conditions. The maternal generation developed at a temperature of 20°C and day length of 12, 16, or 18 h. The progeny generation was incubated at low temperature conditions (6, 9, 12, or 15°C) during 15 or 30 days. Individual variations were statistically significant in most treatments of the experiment, including the cases when the average proportion of diapausing progeny was close to 90%. The distribution of females by the proportion of diapausing progeny was unimodal. When the average proportion of diapausing progeny was about 50%, the distribution was close to normal, i. e. the individual variation was rather quantitative (gradual) than qualitative (polymorphic). The correlation in the proportion of diapausing individuals between the progenies produced by the same female during sequential parasitization of different portions of the grain moth eggs was significantly positive suggesting that the variability in the tendency to diapause was (at least partly) determined by individual characteristics of Trichogramma wasps. Individual variation of females in the proportion of diapausing progeny should be accounted for in the development of the methods for laboratory investigation and mass rearing of Trichogramma species.