Abstract: Hypopi are specialized forms of non-Psoroptidia astigmatid mites that may occur between protonymphal and tritonymphal stages. They are produced to resist the worsening habitat or adverse environmental conditions and to disperse by means of other animals. Their formation and molting are determined by genetic factors and influenced by one or more environmental factors such as temperature, relative humidity, nutrition and density, whose effects differ from species to species. The interaction of genetic and environmental factors plays a key role in the process. Many of these mites are closely related to our lives and have brought difficulties to manage and quarantine due to their highly scleritized cuticle and small size. In view of the importance of the special stage, herein we comprehensively review the research progress in the occurrence, dispersal, formation, molting and control of the hypopi.

Key words: hypopus, development, phoresy, environmental factors, genetic factors, control