Distribution and dispersal of <i>Urophora cardui</i> (Diptera, Tephritidae) in Finland in 1985-1991

Authors

• Antti Jansson

DOI:

https://doi.org/10.33338/ef.83553

Abstract

Urophora cardui (Linnaeus) was reported for the first time from Finland in 1981, from the city of Helsinki. During the years 1985-1991 the distribution and dispersal of the species was monitored by searching for galls which the fly larvae cause on stems of the thistle Cirsium arvense. In 1986 galls were observed at a distance of 18-36 km from the center of Helsinki, and by 1991 the distance had increased to 37-55 km along the main roads. Annual dispersal of the fly was found to correlate strongly with the warmth of summers: after a cold summer the area occupied by the fly actually decreased, but in a warm summer new galls were found up to 16 km further from city center than the year before.