Abstract: According to the fluctuation of population of CiteUus dauricus and its nest flea index in Wuningbatu Sumu, Zhengxiangbai Banner, Inner Mongolia Autonomous Region during 1981-1993, the authors have found that there are ten flea species with CiteUophilus tesquorum mongolicus (45.4%) as the most dominant member, Frontopsyllaluculenta (25.0O%) the second and Neopsylla abagaitui (21.3%) the third. N. bidentatiformis and Ophthalmopsylla praefecta are only of common occurrence whereas otherspecies are rather scarce. The correlation between the host population and its burrow nest flea index is not significant (P>0.10). But the correlation between the host population and the flea infection rate of its burrow nest is significant (P<0.05). The diversity and evenness of flea species seem stable in different years. Furthermore, the correlation between the body flea index and burrow nest flea index is significant (P<0.02), I.E. , burrow flea index=4. 08494-8. 7483 body flea index. The mean value of the burrowflea index is 9.74 times as high as that of the body flea index, and the difference between them is significant (P<0.005).

Key words: rat nest flea index, population density of CiteUus dauricus, Citellophilus tesquorum mongolicus, yearly species fluctuation, species diversity