Animals within a population differ consistently in behavior over time and/or across conditions. A general question is how such differences referred to as personalities are maintained through evolution. One suggested mechanism is a nonrandom mate choice, which has been supported in species in which mate choice associates with direct material benefits. Much less is known about mating patterns and personality in species where males provide only sperm and in which the benefits of female choice are based only on good and/or compatible genes. The bridge spider Larinioides sclopetarius Clerck (Araneidae) exhibits heritable between-individual differences in intrasex aggressiveness. We studied mating probabilities by aggressiveness type of both sexes, and success in sperm competition of aggressive versus nonaggressive males. We staged trials that resemble field conditions: 4 males (2 aggressive and 2 nonaggressive) had simultaneous choice between an aggressive and a nonaggressive female. Although there were no differences in initial approaches of male types toward female types, aggressive males mainly mated with aggressive females, and nonaggressive males more likely mated with nonaggressive females. Female aggressiveness type was not related to fecundity, which may be a consequence of equal food supply in the laboratory. However, in double-mating trials using the sterile-male technique to measure paternity of aggressive versus nonaggressive males, we found that sons of aggressive parents fathered relatively more offspring. We conclude that assortative mating by aggressiveness type might maintain between-individual differences in aggressiveness in L. sclopetarius.

Nephilid spiders are known for gigantic females and tiny males. Such extreme sexual dimorphism and male‐biased sex ratios result in fierce male–male competition for mates. Intense sperm competition may be responsible for behaviors such as mate guarding, mate binding, opportunistic mating, genital mutilation, mating plugs and male castration (eunuchs). We studied the mating biology of two phylogenetically, behaviorally and morphologically distinct south‐east Asian nephilid spider species (Herennia multipuncta, Nephila pilipes) in nature and in the laboratory. Specifically, we established the frequencies and effectiveness of plugging (a plug is part of the male copulatory organ), and tested for male and female copulatory organ reuse. Both in nature and in the laboratory, plug frequencies were higher in H. multipuncta (75–80% females plugged) compared with N. pilipes (45–47.4%), but the differences were not significant. Plugs were single and effective (no remating) in H. multipuncta but multiple and ineffective (remating possible) in N. pilipes. In Herennia, the males plugged when the female was aggressive and in Nephila plugging was more likely when mating with previously mated and larger females. Further differences in sexual biology are complete palpal removal and higher sexual aggressiveness in Herennia (sexual cannibalism recorded for the first time), and mate binding in Nephila. Thus, we propose the following evolutionary hypothesis: nephilid plugging was ancestrally successful and enabled males to monopolize females, but plugging became ineffective in the phylogenetically derived Nephila. If the evolution of nephilid sexual mechanisms is driven by sexual conflict, then the male mechanism to monopolize females prevailed in a part of the phylogeny, but the female resistance to evade monopolization ultimately won the arms race.