Anal secretions of 17 species in nine genera of the subfamily Idolothripinae were analzyed by TLC, GC, and GC-MS. From all species, juglone and two or more carboxylic acids with carbon numbers ranging from 10 to 14 were detected; the exception was Gastrothrips sp., from which none was detected. Twelve carboxylic acids were found, of which decanoic acid, (E)-4-decenoic acid, and (Z)-5-tetradecenoic acid were widely found, and acid ingredients were fairly species-specific. The Gastrothrips sp. was the only exception, and it had no secretion components among the tubuliferan species so far analyzed. Juglone is thought to be a potent defensive allomone, and roles of the carboxylic acids are discussed.