Hoplopleura pacifica is a dominant species of ectoparasitic sucking lice on the body surface of a common rat species, Rattus flavipectus in Yunan province of China. To illustrate the spatial distribution pattern of H. pacifica among the individuals of R. flavipectus, Iwao's linear regression method and a significance test of random deviation for the method were used, and a regression equation was established in the light of Iwao's method. The established equation is M*12.10+4.76M (r0.75, P<0.01) where both α and β are considerably higher than 0 and 1, the border values for determining spatial pattern of populations. The calculated F value is F6.07 (P<0.05) in the significance test of random deviation. The spatial distribution pattern of H. pacifica among the individuals of R. flavipectus is of aggregated distribution. The result suggests that the individuals of H. pacifica have a tendency to congregate together and form different individual groups instead of evenly distributing on the body surface of every rat host.
