Frozen parental care behavior in a pseudoscorpion trapped in Eocene Baltic amber

Direct fossil evidence of behavior is rare, which limits our understanding of the early evolution of social and reproductive strategies. Parental care and phoresy are two important life-history traits in arthropods: parental care can improve offspring survival, whereas phoresy enables small animals to disperse by attaching to larger, more mobile carriers. Pseudoscorpions are a diverse and ecologically widespread group of arachnids, with parental care well documented among living species. However, the fossil record of this behavior remains extremely limited. Here, we report the earliest known evidence for the combined occurrence of parental care and phoresy in pseudoscorpions, preserved in approximately 35-million-year-old Baltic amber. The specimen preserves a female pseudoscorpion carrying a brood sac while attached to a dipteran, apparently grasping one of the fly's hind legs with her left pedipalp. This association shows that brood care and phoretic dispersal were already coupled by the Eocene. It further suggests that phoresy may have allowed brooding pseudoscorpions to disperse while maintaining physical protection of their developing offspring.