In 1957. we discovered a new species of Trombicula in gaohu, Qingtian. mountainous region of south Zhejiang. which is the dominant species in that locality. Its seasonal and geographical distribution are consistent with tbe epidemic of tsutsugamushi disease. The Rickettsia tsutsugamushi had been isolated from the larva hosts and patients at the same time. It was confirmed by epidemiological investigation that this tsutsugamushi is a new vector of tsutsugamushi disease. This Trombicula was discovered first time in Gaohu and was named Trombicula (Leptotrombidium) Caohuensis nov sp. This rteport had been published in 1960.In July 1984. we tested a biting experiment by setting 11 larvae of the tsutsugamushi on our own forearms and confirmed that the Trombicula had the ability of stinging and biting human bodies, and that this ability persisted after the changing of hosts (from mouse to man). This test provided a new evidence of vector effect of Trombicula Caohuensis nov sp in ecology.