The water spider (Argyroneta aquatica) is the only known spider who spend its whole life under water and that is why it differs from its terrestrial relatives.However, its systematic position is highly controversial and remains unresolved since Clerck (1757) described it.It was suggested to be a single group as a family (Argyronetidae), or a subfamily of Agelenidae, Dictynidae and Lycosidae.The newest morphological research suggests that it is a group of Cybaeidae.However, it is not accepted by some arachnologists and close relationship between Argyroneta and Paratheuma (Desidae) is supported by recent molecular phylogenetic analysis.Present viewpoint of its systematic position is really chaotic.With the widespread use of molecular data, the present viewpoint of putting Argyroneta aquatica in Cybaeidae was challenged.Intriguingly, Argyroneta seems to be a clade of Dictynidae.The arrangement of internal terminals among Dictynidae clade in these gene trees suggests that Argyroneta is closely related to or derived from a dictynid-like ancestor.On the basis of recent studies, we performed a phylogenetic analysis with broader sampling of Dictynidae taxa.Using molecular data from both nuclear genes (18S rRNA, 28S rRNA, Histone H3) and mitochondrial gene (CO1), our phylogenetic trees strongly support the sister-group relationship between Argryroneta and Argenna (Dictynidae).Besides, topological tests significantly support the Cybaeidae as monophyletic only when Argyroneta is excluded.Here, we suggest transferring Argyroneta aquatica to Dictynidae.This is also verified by morphological data.By comparing the morphological characters, Argenna patula, Argyroneta aquatica, Tricholathys spiralis, Paratheuma armata, and P.insulana share a very similar appearance and genital pattern: the slender, prolaterally originated embolus, the longer than wide palpal tibia with a strong retrolateral apophysis apically, a retrolaterally located and proximally extended conductor and a pair of widely separated copulatory openings.Additionally, from the evidences of molecular and morphological data, Paratheuma is also suggested to be transferred to Dictynidae.