PUB - Publikationen an der Universität Bielefeld

A recently developed experimental set-up has been used to test the constancy of flight direction in the large white butterfly Pieris brassicae, originally collected in Northern Germany. The night direction, tested with virgin females, depends on the developmental mode. Butterflies from diapause pupae fly north, those from subitan pupae fly south. The constancy of the flight direction has been examined in detail with the spring generation over a period of 14 d. The preferred direction does not change with advancing age and is essentially not influenced by temperature or by the sun's azimuth. The night activity, however, increases with temperature, but this is concealed by an intrinsic response resulting in a diurnal peak of night activity at 10.00-11.00 hours, long before the maximum temperature of the day is reached. Whether the observed direction can be considered as a parameter of migration behaviour is discussed. It is shown that migration in Pieris brassicae does not end with reproductive maturity but lasts throughout the entire imaginal stage.