Theory shows that polyandry (mating with multiple males within a reproductive season) works as bet-hedging to increase the geometric mean fitness (GMF) of polyandrous genotype over generations and avoid extinction but it was rarely tested empirically. In this study, we distributed the eggs of Gryllus bimaculatus females mated with 1~4 males (mating treatment) into 4 petri dishes with different conditions: 25°C/fresh water, 37°C/fresh water, 25°C/salt water, 37°C/salt water, simulating 4 clutches laid at the different sites are suffered environmental change. The egg hatching rate were obtained over 7 blocks with different females for each mating treatment. In general, significantly more eggs hatched in 25°C than 37°C and in fresh water than salt water. The reproductive failure (no hatched eggs per petri dish) frequently occurred in monandry and 2-male polyandry. Next, we considered 7 blocks as the successive 7 virtual generations and calculated the within-generation arithmetic mean fitness (AMF) among females of the same treatment and the between-generation GMF of the AMF across 7 generations. Randomization test shows that the GMF of 3- and 4-male polyandry were significantly higher than monandry. This study shows that the risk from mating only once can be avoided by polyandrous mating as bet-hedging.

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Out of collected eggs (200 eggs from a mother as a standard), the number of fertilized, eye-spot appeared and hatched eggs are recorded. The procedures to calculate and compare within-generation (between-mothers) arithmetic mean fitness and between-generation geometric mean fitness for monandrous and 2~4 male polyandrous strategies across 7 blocks (virtual generations) are shown.