抄録
Characteristics of heteromorphic deutonymphs of non-psoroptid astigmatid mites were reviewed. The duetonymph was called hypopus since recognized as belonging to the genus“Hypopus”in Mesostigmata, then as one of immature stages in Astigmata. Morphology is far different from the other stages, no functional mouth part, short and stout legs, adapted stmctures for phoresy and so on. Such differences caused taxonomic difficulty in this group. Deutonymphal formation is generally induced by adverse environmental conditions, which it should resist or escape from. Although stimuli to molt to next stage might be different in each species, environmental changes including food supply are necessary for development. The deutonymph, which may represent specific relationships between phoretic hosts exploits other organisms to migrate into new environment. In applied fields, importance of the deutonymph has not been fully understood.
