STRUCTURE AND DENSITY OF LUCERNE POLLINATING WILD BEE POPULATIONS AS AFFECTED BY CHANGING AGRICULTURE

摘要

Intensive surveys were made on Lucerne pollinating wild bee populations in Hungary in the mid-fifties (Moczar), late sixties (Benedek), and early seventies (Tanacs). Comparing these surveys, a dramatic change in the structure of Lucerne pollinating wild bee populations occurred between the fifties and the sixties. The density of some bee species reduced, other species remained unchanged, while the density of Medicago oligoleges increased. The phenomena is explained by changing agricultural land usage since the fifties and included a rapid increase in field size as well as an increased use of mechanical weed control along road sides and balks and by an increased use of herbicides on arable land. The effects are discussed in terms of the seasonal occurrence for different groups of wild bees. It is concluded that the changes in agriculture were favorable for some bee species, but were unfavorable for other species.