- Summary 1 We have assessed how different host parameters affect species richness of flea assemblages using the independent contrasts method. Three groups of host parameters were examined. The first group included host body parameters (body size, basal and average daily metabolic rates), the second group included parameters of geographical range size and position of this range in relation to the equator (latitude) and the third group comprised parameters related to the number of sympatric closely related species. 2 None of the host body parameters correlated with species richness of flea assemblages. 3 Flea species richness increased with an increase in latitude of the geographical range centre of a host as well as with an increase in a composite variable that described the size of the geographical range. 4 The number of sympatric closely related species both across the entire geographical range and locally was correlated positively with species richness of fleas. 5 Our results show that species richness of ectoparasites is affected little by parameters of the host body and to a greater extent by parameters related to the host environment.