Immunity is an important mechanism of protection against pathogens and parasites. One factor that can influence immunity is mating. During mating, male-derived materials are transferred to females, and the physical contact also involves the potential risk of sexually transmitted infections, and wounding. Thus, mating can challenge a female’s immune system. This review focuses on exploring how immunity and mating interact in female insects. Although mating has been shown to cause female immune responses in several species, the responses do not always match the observed resistance to pathogens/parasites. Mating up-regulates female immune responses while female resistance is reduced compared to virgin females in some species, and vice versa in other taxa. We discuss why mismatches occur and why post-mating female resistance differs among species, and suggest that measured immune responses may not correlate with female resistance. Also, the mating system will play a major role. Polyandrous mating systems can generate intense post-mating sexual conflict, which can impose high costs of mating on females. Reduced female post-mating resistance may be due to direct suppression of female immunity by males. Alternatively, polyandry may increase the risk of sexually transmitted infections. If this is the major factor driving female post-mating resistance, females of polyandrous species should have higher post-mating immunity. To date, there are insufficient numbers of studies to fully answer the question ‘does mating negatively affect female immune defences in insects?’ To elucidate the links between immunity and mating in females, we need more studies in more species with varied mating systems.

We experimentally tested the indirect and direct effects of Amblyseius womersleyi on Tetranychus kanzawai. The presence of A. womersleyi indirectly reduced egg production of T. kanzawai by 25.9%, although this effect had less impact than direct egg predation. The mechanism of this indirect effect could be explained by behavioral changes in T. kanzawai females; in the presence of A. womersleyi, T. kanzawai females allocated more time to seeking refuge on webs at the expense of feeding on leaves.

Infertility is common in nature despite its obvious cost to individual fitness. Rising global temperatures are predicted to decrease fertility, and male sterility is frequently used in attempts to regulate pest or disease vector populations. When males are infertile, females may mate with multiple males to ensure fertilization, and changes in female mating behavior in turn could intensify selection on male fertility. Fertility assurance is a potentially wide-spread explanation for polyandry, but whether and how it actually contributes to the evolution of polyandry is not clear. Moreover, whether a drop in male fertility would lead to a genetic increase in polyandry depends on whether females respond genetically or through behavioral plasticity to male infertility. Here, we experimentally manipulate male fertility through heat-exposure in Drosophila pseudoobscura, and test female discrimination against infertile males before and after mating. Using isogenic lines, we compare the roles of behaviorally plastic versus genetically fixed polyandry. We find that heat-exposed males are less active and attractive, and that females are more likely to remate after mating with these males. Remating rate increases with reduced reproductive output, indicating that females use current sperm storage threshold to make dynamic remating decisions. After remating with fertile males, females restore normal fecundity levels. Our results suggest that male infertility could explain the evolution of adaptively flexible polyandry, but is less likely to cause an increase in genetic polyandry.

No abstract

Prenatal maternal effects on diapause induction were examined in the tetranychid mites, Tetranychus urticae and T. kanzawai. In T. urticae, the incidence of diapause of offspring whose mothers had experienced short daylength (9L15D) was higher than that of the offspring whose mothers had experienced long daylength (16L8D) when the offspring developed under short daylength. However, this maternal effect was not conspicuous when the offspring developed under long daylength. The incidence of diapause in T. urticae offspring was higher when their mothers had experienced a high density during the juvenile period. By contrast, the photoperiod and density experienced by mothers did not affect the incidence of diapause in the offspring of T. kanzawai. However, the presence of senior female adults on the same leaf during the juvenile period enhanced the incidence of diapause in T. kanzawai. The difference in maternal effects observed between T. urticae and T. kanzawai is discussed with respect to their life-history characteristics.