Studies on Spatial Pattern of Chigger Mite Populations on Small Mammals in the Surrounding Areas of Erhai Lake in Dali of Yunnan

Objective To study the spatial pattern of the chigger mite populations on the body surface of small mammals in the surrounding areas of Erhai Lake in Dali of Yunnan, China. Methods Coefficient(C), clumping index(I), Cassie index(C_A) and patch index( m~/m ) were used to analyze the spatial patterns of chigger mite populations. Results The captured 3 313 small mammals were identified as 21 species and 14 genera in 7 families. 56 150 individuals of chigger mites were collected from the two auricles of 3 313 small mammal hosts and they were identified as 109 species and 13 genera in 3 subfamilies of Trombiculidae. Eight main species of chigger mites were selected as target and the spatial pattern of eight main species of chigger mites (populations) were measured among different individuals of six species of small mammals. The results reveal that all the numeric values from four kinds of indices (C, I, C_A and m~/m) are much higher than their border values (0 or 1) and the spatial distribution patterns of eight main chigger mite populations are therefore determined as the aggregated patterns of distribution among the different individuals of their hosts, small mammals. Conclusion The studied chigger mites from the surrounding area of Erhai Lake in Dali of Yunnan neither evenly nor randomly distribute among the different individuals of their small mammal hosts, but aggregately gather on the body surface of some hosts, forming aggregated ectoparasitic groups of the mites on small mammal hosts.