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Intersexual and intrasexual selections are important driving forces that lead to diversification of sexual characteristics. Tetragnatha spiders have elongated chelicerae and sexual dimorphism in chelicera length whose magnitude varies among species. Because they use their chelicerae during copulation and as weapons in male–male competition, this divergence reflects repeated intersexual and intrasexual selection. To infer the causes of chelicera length diversity, we examined the roles of the elongated chelicerae in copulatory behavior of a Tetragnatha species and clarified the interspecific sexual dimorphism of chelicera length in 15 species. The longer chelicerae of female Tetragnatha allowed females to kill males, suggesting female rejection of mating using the elongated chelicerae. Comparisons based on independent contrasts showed that chelicera length was significantly positively correlated between the sexes across species, possibly reflecting sexually antagonistic coevolution of male and female chelicera lengths. However, some species showed male-biased sexual dimorphism, indicating that intrasexual selection (male competition) may be more important than intersexual competition in some species. Our results demonstrate that both intersexual and intrasexual selection led to interspecific variation in sexual dimorphism of chelicera length in this group. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships between genera of the Polysphincta group of Pimplinae (Ichneumonidae) were surveyed using molecular markers, partial sequences of cytochrome c oxidase I ( COI), 28S rRNA and elongation factor 1α, and maximum likelihood and Bayesian approaches to obtain a robust phylogenetic hypothesis to understand the evolution of the group. The Polysphincta group was recovered as monophyletic, although relationships between genera were different from previous hypotheses based on morphological data. Within the Polysphincta group, three major clades were recognized and phylogenetic relationships among them were well resolved as ( Schizopyga subgroup + ( Acrodactyla subgroup + Polysphincta subgroup)). The Schizopyga subgroup consisted of the genera Piogaster, Schizopyga, Zabrachypus and Brachyzapus. As the genus Schizopyga was found to be polyphyletic, the genus Dreisbachia, which had been synonymized under Schizopyga, was resurrected and Iania gen.n. is proposed for Dreisbachia pictifrons, to maintain monophyletic genera. Species of the Schizopyga subgroup utilize spiders constructing egg-laying chambers or funnel webs as hosts. The genus Piogaster was not recovered as the sister to all other members of the genus group, unlike previous hypotheses, but was nested in this clade as ( Zabrachypus + (( Brachyzapus + Schizopyga) + ( Dreisbachia + ( Iania + Piogaster)))). Members of the Acrodactyla and Polysphincta subgroups attack spiders that weave aerial webs. The host range of the former is centred on tetragnathid and linyphiid spiders, the host range of the latter seems to centre mainly on orb-weaving araneids and partly on theridiids weaving three-dimensional ( 3D) irregular webs. Based on the obtained phylogeny of the group, the evolution of larval and cocoon morphology, and the mode of parasitism are discussed. Acrodactyla varicarinata Uchida & Momoi and A. inoperta Kusigemati are transferred to the genus Megaetaira ( comb.n.). This published work has been registered in ZooBank, . [ABSTRACT FROM AUTHOR]