The study of bee diversity and activity was conducted from January until June 1994 in a natural vegetation parcel (6200 m2) in Constantine (Algeria). The results showed the presence of 10 genera of wild bees visiting natural flowers and belonging to four families: Andrenidae, Anthophoridae, Halictidae, and Megachilidae. The Apidae family was represented by honeybee (Apis mellifera L.) and bumblebee (Bombus ruderatus siculus Dalla Torre et Friese). Census of bee populations revealed the abundance of wild bees with 66.26% of flowers visits, honeybee with 31.98%, B. ruderatus and Xylocopa violacea with 1.59 and 0.17% of total fauna, respectively. The beginning flight activity of these species started from a minimum threshold of temperature and humidity. The alimentary specialization was quantified by Simpson’s diversity index (Is) and by Shannon’s diversity index (Ish). Apis mellifera had the highest floral visits index (Is = 0.866) and the broadest alimentary niche index (Ish = 0.316).