Small sweat bees (Hymenoptera: Halictidae) as potential major pollinators of melon (Cucumis melo) in the Mediterranean

In the current scenario of a general decline of the honeybee worldwide, studies on the potential of alternative bee species in pollinating cultivated plants are important. Although melon, Cucumis melo, is a crop with great commercial importance, there is very little information on its pollinating fauna in Europe, and none from the southern Mediterranean area. In a locality in central Spain, using both pan-traps and net collections, we found that melon flowers are visited by 31 species of bees spanning four families, though only four were both dominant and constant. These four species belonged to the family Halictidae (sweat bees) and mostly (three species) to the genus Lasioglossum. Five other species could be defined as accessory: honeybee, Apis mellifera, and four other halictids. Individuals of the dominant species were smaller, on average, than those from all the other species. Observations on the frequency of pollen and nectar foraging and on flower visit duration further suggested L. malachurum as the potential key pollinator. Females of this species started to forage on melon early in the flowering season and exhibited two activity peaks in summer, thus covering the whole season. Although in other sites across continents melon seems to be more heavily pollinated by honeybees, this seems to be not the case in the Mediterranean, where sweat bees seem to be the major pollinators of this crop