Caeculisoma pouyani Noei and Kohansal sp. nov. (Trombidiformes: Erythraeidae) ectoparasitic on Sphodromerus luteipes Uvarov (Orthoptera: Acrididae), an unidentified Cicadellidae nymph (Hemiptera: Auchenorrhyncha) and an unidentified species of Miridae (Hemiptera: Heteroptera) in Chahkandan and Zahan villages, Birjand, South Khorasan province, Iran, is described and illustrated. The newly described species is the first representative of the genus Caeculisoma Berlese in Iran. A key to the larval species of Caeculisoma of the world is updated.