Bean weevils (Coleoptera: Chrysomelidae: Bruchinae) are responsible for large quantity losses of cowpea (Vigna unguiculata (L.) Walp.; Fabaceae) and common bean (Phaseolus vulgaris L.; Fabaceae). The magnitude of damage is related to the grains' varietal susceptibility. The objective of this study was to determine the population development rates of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) in 4 landrace varieties of cowpea (var. ‘UFAC-B01,' ‘UFAC-MV01,' ‘UFAC-MG01,' and ‘UFAC-Q01'), as well as the population development rates of Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae) in 4 landrace varieties of common bean (var. ‘UFAC-G01,' ‘UFAC-M01,' ‘UFAC-P01,’ and ‘UFAC-R01'). We determined the population development rates of the weevils in each variety. The weight of 100 grains (g) and the percentage of grain weight loss were measured, and correlations between these variables were analyzed. The statistical design was completely randomized, with 4 replications. Varieties UFAC-Q01 (cowpea) and UFAC-R01 (common bean) showed lower insect population development rates than other varieties. Although variations were found in the weight of 100 grains and grain weight loss, no significant correlations with bean weevil population development were observed. The cowpea and common bean landrace varieties from the southwestern Amazon region are important sources of resistance to bean weevils. The UFAC-Q01 cowpea variety and the UFAC-R01 common bean variety showed lower susceptibility to C. maculatus and Z. subfasciatus, respectively.