Variations in the “spontaneous” dynamics of the tendency to diapause among generations of Trichogramma telengai Sor. (Hymenoptera, Trichogrammatidae)

Variations in the tendency to diapause were investigated in 5 successive generations of 6 parthenogenetic clones of Trichogramma telengai Sor. reared under constant laboratory conditions (the temperature of 20°C and the day length of 18 h). The tendency to diapause was estimated by the proportion of the progeny which diapaused at temperatures of 13, 14 and 15°C. Although the variations in the tendency to diapause in successive generations of different clones were positively correlated, the dynamics of the proportion of diapausing progeny in one of the studied clones was significantly different from that in the other clones reared under the same conditions. Moreover, the differences among subclones originated from the same female were also revealed. Analysis of the results suggests that the interclonal variations in the proportion of diapausing progeny were at least partly caused by endogenous factors. The differences between clones can arise during the development of one generation but can also damp very fast or, at least, they are not accumulated over generations. These variations are probably based on the same epigenetic mechanisms that form the basis of the maternal effect on the progeny diapause in Trichogramma species.