Female mating failures in insects

Empirical and experimental studies reporting the probability that some females remain unmated in field populations of insects (defined herein as mating failures) are reviewed in more than 100 species. The techniques used to quantify mating failures in the field are summarized, as well as factors that influence the probability that females mate during their lifetime. The existing empirical data provide partial support for hypotheses generated by theoretical models, although the trends observed in field populations are far more diverse and complex than predictions derived from ecological theory, e.g., the effect of population density on female mating success at small and large spatial scales is opposite. Mating success of females increases with the ratio of males in the population, but the relation between emergence time, sex ratio, and female mating success is variable. Females have evolved a broad range of physiological and behavioural adaptations to reduce mating failures, and exhibit a flexible context-dependent response to constraints limiting mating success. The large number of studies in Lepidoptera suggests a higher mating success in butterflies than moths. Examples of high rates of mating failure include species with gynogenous reproduction, long range migration, pre-reproductive maturation, male-biased sex ratio, acquisition of resources essential for reproduction, and female flightlessness. Species with sessile females that mate and oviposit near their emergence site provide model systems to investigate the causes and demographic consequences of female mating failure.