Objective: To compare the morphological characteristics of two sibling species of chigger mites: Leptotrombidium
rubellum and Leptotrombidium deliense. Methods: 100 identified larvae of two mite species(L. rubellum and L. deliense)with clear
structure were collected from the body surface of Asian house rat, Rattus tanezumi(R. flavipectus), whose morphological structure were
observed and measured under a microscope for analyzing the morphological difference between two sibling species. Results: L.
rubellum had a quadrate-like scutum(SB<AP), but L. deliense had a rectangle-like scutum(SB>AP), and the difference between
them had statistical significance(P<0.01). The SD, SB range of L. deliense is rather wider, and its SD, SD width/length, SB, PSB,
PW/AP, PW value were all slightly higher than L. Rubellum(P<0.05). Conclusion: The two mite species are very close to each other
morphologically with tiny differences. Compared with SB<AP in L. rubellum, the difference of L. deliense is SB>AP, and this difference
can be used as the key evidence to differentiate the two mite species.