The Solifugae, commonly known as camel spiders, represent an underexplored group of arachnids characterized by a significant diversity in genital morphology, which is likely associated with functional diversity. However, the copulatory mechanics of this group has not been empirically investigated for any species. In this study, we examine for the first time the copulatory mechanics of a Solifugae species, Syndaesia sp., an Argentinian species noted for its complex genital morphology, utilizing microCT data of a cryofixed mating pair. Our findings reveal that Syndaesia sp. males hydraulically manipulate their intromittent flagellum—a prominent structure on the male chelicerae—during sperm transfer while maintaining a firm genital clasp with the chelicerae. The flagellum is deeply inserted into the female reproductive system, reaching the oviduct. The insertion is crossed, with the left flagellum inserted into the right oviduct, suggesting a sequential insertion of the flagella. Although sperm transfer was not observed owing to the mating pair being fixed at an early stage of copulation, several hypotheses regarding sperm allocation are discussed based on the morphology and insertion pattern of the flagellum, thereby setting the stage for future investigations into the function and evolution of camel spider genitalia.
Dante Poy, Hernán Iuri, Andrés Ojanguren-Affilastro, Alfredo Peretti, Peter Michalik; First characterization of copulatory mechanics in camel spiders (Solifugae) using microCT. R. Soc. Open Sci. 1 July 2026; 13 (7): rsos260582. https://doi.org/10.1098/rsos.260582
