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Trichadenotecnum is one of the most diverse genera among the non-parasitic members of Psocodea (Insecta: "Psocoptera"). The genus shows a world-wide distribution (excluding the Australian Region, where only one introduced species is known) with its center of diversity in southern to eastern Asia. Several species groups had been proposed for this large genus based on morphology, but their validity and phylogenetic relationships are still unclear because of great morphological diversity in the genitalia, systematically the most relevant character. In this study, we estimated the molecular phylogeny of the Old World species of Trichadenotecnum based on extensive taxon sampling. As a result, the monophyly of morphology-based species groups was very strongly supported in most cases. However, two groups were recovered as non-monophyletic, which had been inadequately defined on the basis of plesiomorphies or convergences of genital characters. First, the monophyly of the sexpunctatum group was not supported because the medium group was found to be embedded within this group. The simpler genitalia observed in the medium group were considered to be derived from the more complicated genitalia present in the sexpunctatum group. Second, the monophyly of the majus group was not supported for two reasons: (1) It was divided into two distant clades which initially had been united on the basis of convergent similarities of the male genitalia. (2) Two species groups were revealed to be embedded within the main clade of the majus group; the initial separation of these groups had been based on reversals to the ancestral genital condition.

SummarySex-specific elaborations are common in animals and have attracted the attention of many biologists, including Darwin [1]. It is accepted that sexual selection promotes the evolution of sex-specific elaborations. Due to the faster replenishment rate of gametes, males generally have higher potential reproductive and optimal mating rates than females. Therefore, sexual selection acts strongly on males [2], leading to the rapid evolution and diversification of male genitalia [3]. Male genitalia are sometimes used as devices for coercive holding of females as a result of sexual conflict over mating [4, 5]. In contrast, female genitalia are usually simple. Here we report the reversal of intromittent organs in the insect genus Neotrogla (Psocodea: Prionoglarididae) from Brazilian caves. Females have a highly elaborate, penis-like structure, the gynosome, while males lack an intromittent organ. The gynosome has species-specific elaborations, such as numerous spines that fit species-specific pouches in the simple male genital chamber. During prolonged copulation (∼40–70 hr), a large and potentially nutritious ejaculate is transferred from the male via the gynosome. The correlated genital evolution in Neotrogla is probably driven by reversed sexual selection with females competing for seminal gifts. Nothing similar is known among sex-role reversed animals.

The unusually developed head surface sculpture of a Pakistan strain of the stored-product psocid Liposcelis paeta was discovered using scanning electron microscopy (SEM). The morphologically unique serrate tubercle sculpture observed was previously unknown in the genus Liposcelis. The typical morphological female and male characteristics, which are important for species diagnosis, were described and visualised with SEM micrographs. The vertex sculptures of various geographic strains of L. paeta and of some species belonging to all known species-groups of the genus Liposcelis were compared to assess the extent of variability. Molecular data for L. paeta geographic strains are analysed and the taxonomic positions of these geographic strains are also discussed.