AN EMPIRICAL-MODEL OF DIAPAUSE STRATEGIES OF THE CRICKET ALLONEMOBIUS-SOCIUS

We modeled the effect of heterogeneity in growing-season length on the diapause strategies of a partially bivoltine population of the stripe d ground cricket Allonemobius socius. First-generation females of this population can lay mixtures of direct-developing and diapause eggs, a nd bet-hedging theory predicts that in an unpredictably variable envir onment the proportion of diapause eggs laid will gradually increase ov er the season as the likelihood that a second generation will be able to complete development before winter decreases. We quantified variabi lity in the thermal regime using long-term meteorological records, and constructed an analytical model using empirical components for growth and reproduction. The model predicted that females should switch to d iapause egg production in early August, a finding that was corroborate d by experimental and field observations. The form of the switch betwe en egg types predicted by the model was a transition that spanned only a few days and was similar to that estimated from a laboratory experi ment. Thus interannual variation in climate was not sufficient for the evolution of a marked bet-hedging response in the form of a gradual i ncrease in the proportion of diapause eggs. However, we observed consi derable variation among females in their diapause strategies that rema ins unexplained.