Mesostigmata

order of arachnids Mesostigmata (Mesostigmata) is an order comprising closely related families of organisms. It contains 11 families with 23 known species. Key family groups include Dermanyssidae, Haemogamasidae, Halarachnidae, Laelapidae, Macrochelidae, and Macronyssidae. It belongs to Arachnids (Arachnida).