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Ectoparasitic insects and mites on Yunnan red-backed voles (Eothenomys miletus) in Dali prefecture, Yunnan Province, southwest China, were studied between 2003 and 2004. In total, 34,389 individuals of 86 species of ectoparasitic insects (seven species of fleas and five species of sucking lice) and mites (23 species of gamasid mites and 51 species of chigger mites) were collected from 916 individual hosts. The diversity of ectoparasites on this single rodent species in such a small area was much higher than in previous reports, which concerned more host species and greater geographical areas. The majority of the ectoparasites were chigger mites, which accounted for 59.3% of the parasite species and 87.4% of the individual parasites. Most voles harbored parasites with an overall prevalence (P) of 82.5% and mean abundance (MA) of 37.5 parasites per host. The dispersion coefficient (C) and patchiness index (m*/m) were used to study the spatial patterns of the seven dominant parasite species, and all seven had aggregated distributions. The species abundance distribution of the ectoparasites on the vole was fitted by Preston's lognormal distribution (R (2) = 0.82), and the total expected parasite species was estimated from this plot as 167 species. Yunnan red-backed voles harbor many ectoparasites as revealed by examination of a large host population. Future field investigations should sample large numbers of host individuals to assess ectoparasite populations.

Objective: To understand the species, species distribution, the dominant species and their interspecies interaction of chigger mites on Eothenomys miletus(a dominant species of rats) in Yunnan., Method: The rats were captured with mouse traps in 16 counties (or cities) during 2000-2004. All mites on the surface of two auricles of the hosts were collected and identified. The patch index (m*/m) and the coefficient of association (V) were adopted to judge the spatial distribution patterns and interspecies interaction of the dominant chigger mite species among different individuals of the rats (E. miletus)., Results: 1157 individuals of E. miletus were captured from 16 counties (citys). 37613 chigger mites (belonging to 3 subfamily, 9 genus and 80 species) were collected from the auricles (body surface) of 1157 rat hosts with a high "overall mite infestation rate" (68.2%) and "overall mite index" (32.5). Six species of mites were found dominant on E. miletus: Leptotrombidium scutellare, Leptotrombidium sinicum, Helenicula simena, Leptotrombidium eothenomydis, Herpetacarus hastoclavus and Leptotrombidium hiemalis. The distribution of the chigger mites among different individuals of E.miletus showed an aggregation pattern. Both positive and negative association existed between each two dominant species of chigger mites., Conclusion: The species composition of chigger mites on Eothenomys miletus is complex with abundant individuals, which reflects a high species diversity of the mites. The main species of chigger mites tend to an aggregation on the body surface of E. miletus.