Outbreak undfirst record of Oxycarenus lavaterae (Fabricius, 1787) (Heteroptera, Lygaeidae) in Northern Switzerland. - In autumn and winter 2004/05 an outbreak of the Mediterranean bug Oxycarenus lavaterae was observed on linden (Tilia) trees in the city of Basel. While this bug has been known for a long time from southern Switzerland, this is the first record north of the Alps in Switzerland. The bugs overwintered in large colonies of up to one meter length on trunks and branches of the trees and, in autumn, locally even posed a transient nuisance to people by crowding park benches and walls of buildings. The distribution, biology and significance of O. lavaterae are discussed.