Transgenerational effects of multiple mating in Spodoptera litura Fabricius (Lepidoptera: Noctuidae).

Polyandrous mating can result in sexual conflict and/or promote the evolution of mating patterns. Does multiple mating by females support the genetic benefits hypothesis and can it be validated as an evolutionary strategy? If we are to decipher the consequences of sexual interactions and understand the interplay of sexual conflict and multiple generational benefits, the transgenerational effects need to be followed over multiple generations. We investigated the effects of three mating patterns, single mating, repeated mating, and multiple mating, on parental Spodoptera litura copulation behavior, and then identified the impact on the development, survival, and fecundity of the F1 and F2 generations. Fecundity was not significantly affected in the F1 generation but was substantially enhanced in the F2 generation. There was a reversal of offspring fitness across the F2 generations from the F1 generations in progeny produced by multiple mating. In addition, the intrinsic rate of increase, finite rate of increase and net reproductive rate in the F1 generation the multiple mating treatment was significantly lower than in the single mating treatment, but there was no apparent effect on the F2 generation. Repeated mating had no significant effects on progeny fitness. We postulate that multiple mating imposes cross-transgenerational effects and may ultimately influence multigenerational fitness in S. litura.

Population Parameters and Feeding Preference of Spodoptera litura (Lepidoptera: Noctuidae) on Different Asparagus officinalis Tissues.

Spodoptera litura is an important pest that seriously affects Asparagus officinalis production. To clarify the population characteristics and feeding preference of S. litura on different asparagus tissues, asparagus stems and leaves were selected as the research objects, related studies were conducted by constructing the life table and the feeding preference experiment. The results showed that S. litura could complete its development and reproduction normally on asparagus stems or leaves. Although the adult longevity and fecundity of S. litura on the two types of tissues were not significantly different, the development duration of larvae and pupae, and total preoviposition period on leaves were significantly longer than those raised on stems. The intrinsic rate of increase and finite rate of increase were 0.186 d-1 and 1.204 d-1 on stems, which were significantly higher than those fed on leaves (0.161 d-1 and 1.175 d-1). The mean generation time on stems (32.88 d) was significantly lower than on leaves (36.88 d). It indicated that stems were more suitable for its population growth. In the feeding preference, the third and fifth instar larvae preferred to feed on leaves, and other instar larvae (except for the sixth instar of 2.5 h) had no significant difference. These results will provide a theoretical reference for further research and forecasting and integrated control.

Does Larval Rearing Diet Lead to Premating Isolation in Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)?

Host plant preference during the larval stage may help shape not only phenotypic plasticity but also behavioral isolation. We assessed the effects of diet on population parameters and mate choice in Spodoptera litura. We raised larvae fed on tobacco, Chinese cabbage, or an artificial diet, and we observed the shortest developmental time and highest fecundity in individuals fed the artificial diet. However, survival rates were higher for larvae on either of the natural diets. Population parameters including intrinsic rate of increase and finite rate of increase were significantly higher with the artificial diet, but this diet led to a lower mean generation time. Copulation duration, copulation time, and number of eggs reared significantly differed between diets. In terms of mate choice, females on the artificial diet rarely mated with males fed on a natural host. Our results support the hypothesis that different diets may promote behavioral isolation, affecting mating outcomes. Thus, findings for populations fed an artificial diet may not reflect findings for populations in the field.

Delay in Mating Reduces Reproductivity but Increases Life Span in Tobacco Cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae).

A pheromone-mediated mating disruption is a vital tool in the management of insect population dynamics that not only prevents mating but also delays mating in the target insect. Here, we examined the effect of delayed mating on the longevity and reproductive performance of the global pest, Spodoptera litura Fabricius (Lepidoptera: Noctuidae). Delayed mating was imposed on both sexes simultaneously, males only, and females only. The results showed that a 30-40% reduction in the successful mating rate of S. litura was caused by 7-d delay in mating. Increased mating ages of both sexes of S. litura resulted in a significant decrease in 3-d-old delayed mating, followed by an increase in mean duration of copulation. Furthermore, delayed mating had a significantly negative influence on the number of S. litura eggs produced. Mating delay imposed on both sexes simultaneously had a significantly greater effect on longevity and the number of eggs than when it was applied to either sex alone, and females were more severely affected by delayed mating than males in terms of longevity. Percentage of mating, fecundity, and female longevity were all significantly correlated with the number of days delayed mating. However, the hatching rate of eggs was not significantly affected by an increased delay in mating. Overall, our results indicated that delayed mating in both females and males drastically reduced the females' reproductive output, which itself was affected more by increasing the age at mating of females than males.