The effect of area size, number of collecting hours and months surveyed, on the estimation of relative richness of bees is analized. In order to characterize a biogeographical region, it is suggested to collect various samples of no less than 400 especimens for each one, in contrasting localities within a region, utilizing the usual standardized methodology for wild bees collecting. Thus, it is possible to have a better profit of the effort invested in the survey, making it possible to estimate the relative species richness among different biogeographical regions, in shorter periods of time.