We describe the spectrum of visitors of seven Mediterranean legumes and identify the potential pollinators by observing insects’ behavior on flowers. The diversity of each population’s insect assemblage (flower visitors and potential pollinators) is calculated in order to estimate to which degree pollination systems are specialized. The importance value (PI) for main taxa of potential pollinators is computed considering both insect fidelity and relative abundance. Different values of importance and dominance characterize pollinator assemblages, revealing various degrees of plant–pollinator specificity despite common papilionaceous floral traits. Visitors’ and pollinators’ diversity was negatively correlated with fruiting success, while there was a positive relation between maximum pollinator importance value and fruit set, suggesting the tendency towards a positive relationship between pollinator specificity and reproductive success.