The weevil Aubeonymus mariaefranciscae is an important pest of sugar beet crops in southern Spain that was first described as a new species in 1979. We have studied the genetic variability of this insect by RAPD analysis of 122 individuals using eight primers. The high resolution provided by random amplified polymorphic DNA (RAPDs), in combination with efficient genetic distance estimators, allowed a very detailed description of the ecology and evolution of the populations of this insect in the south of Spain. The results are compatible with a unique event of colonization, followed by the spreading of the weevil across the surrounding areas. A comparison of the results obtained with different genetic distance estimators is presented. RAPD is shown to be a powerful technique for reconstructing the phylogenetic history of insect populations, even if they have diverged recently, which seems to be the case for A. mariaefranciscae.