Functional morphology of Trichadenotecnum male and female genitalia analyzed using μCT (Insecta: Psocodea: Psocomorpha).

Although the great genital diversity of the barklouse genus Trichadenotecnum has been described in previous studies, the specific function of the genital structures during the copulation process has received less investigative attention. We reconstructed 3D-models of each structure of the male and female genitalia of Trichadenotecnum incognitum in copula and those of uncopulated male and female of Trichadenotecnum pseudomedium. By comparing the changes in male and female genital structures and related muscles in copulated and uncopulated states, the function of each genital structure can be described. During the copulation, we found that the female subgenital plate was hooked into the male body by the distal process on the male paraproct and was fixed by the male epiproct, hypandrium and phallosome. In addition, sexual coevolution was suggested by tightly contacting structures, that is, thorny male hypandrium and thickened membrane around the female spermapore plate. These results not only give us a new understanding copulation process of Trichadenotecnum, but also explain the reasons why genital structures are so divers in the genus.