SPATIAL PATTERN ANALYSIS OF XENOPSYLLA CHEOPIS (SIPHONAPTERA:PULICIDAE) ON ITS DOMINANT RAT HOST,RATTUS FLAVIPECTUS IN THE FOCI OF HUMAN PLAGUE IN YUNNAN,CHINA*

Abstract Xenopsylla chewpis is the main transmitting vector of plague in the foci of human plague in Yunnan China, where its dominant rat host is Rattus flavipectus Spatial distribution pattern of X. cheopis among the individuals of R fluvipectus is studied. Iwao's linear regression method and a significance test of random deviation for the method were used. in the light of Iwao's method, a regression model was established. The model is M =α+βM = 4.0064 + 2.0153M where both α and β are considerably higher than 0 and 1 respectively, the border values for determining spatial pattern of populations. The calculated F value is 4, 5892 (P<0.05) in the significance test of random deviation. The spatial pattern of X. cheopis among the individuals of its dominant host R flavipectus is of an aggregate distribution. The aggregated distribution pattern means that the flea individuals do not evenly distribute on rat host but gather as different size groups on rat individuals. This uneven distribution further suggests that the transmitting opportunity is not always the same even if the frequency of contacting the same species of infected rat, R flavipectus is the same.