AbstractThis paper focuses on the differentiation of specimens, identified asPhytoseiulus longipes, collected in four countries: Argentina, Brazil, Chile and South Africa. Two of these populations are known to feed and develop onTetranychus evansi, whereas the two others do not. As morphologically similar specimens can sometimes belong to different species and because differences in predatory behaviours exist among the four populations considered, we tested for the presence of cryptic species. Morphological and molecular experiments (12S rDNA) were carried out. The four studied populations ofP. longipescould be morphologically differentiated thanks to a combination of characters. However, these morphological differences are very small. The two populations that feed and develop onT. evansi(from Argentina and Brazil) are morphologically closer to each other than to the two other populations. Genetic distances among the four populations ofP. longipeswere very low, suggesting that despite their different feeding habits, all specimens belong to the same species. However, the populations associated withT. evansishowed some genetic differentiation from those that do not use this pest. This is the first time that this type of differentiation has been reported for the family Phytoseiidae. These results are of primary importance to ensure the success of biological control programs and to develop strains adapted to both crops and prey species.