Fotblomflugor Platycheirus (Diptera, Syrphidae) längs den svenska fjällkedjan: en flerårig inventering.

The fauna of hoverflies in Boreal and Arctic parts of Scandinavia is still very poorly investigated. Therefore we performed an 11 year survey of the hoverfly genus Platycheirus Lepeletier & Serville, 1828 along the Caledonian mountain chain in Sweden (from Varmland northwards to the Tornetrask area). During 2003-2013 we annually performed two trips in order to survey various areas and to collect flies by netting. Altogether 150 localities were visited and a total of 1862 Platycheirus-specimens belonging to 40 species were collected. Two species were recorded for the first time in Sweden: Platycheirus carinatus(Curran, 1927) and P. magadanensis Mutin, 1999 and 74 records were new for various fauna-provinces. Four main areas were selected for comparative studies on distribution, habitat, local migration and environmental influences on population fluctuation of Platycheirus-species. We noted that males hatch earlier than females and the latter sex await the maturing anthers of their feeding plants. Moreover, Platycheirus-species in alpine and subalpine terrain seem to be very cold resistant and active at air-temperatures around 10O C. Environmental disturbance within the subalpine and northern boreal vegetation zones, e.g. cutting of woods or constructing of slalom slopes, creates new flower rich habitats and therefore support the population sizes within this assemblage of overflies. The observed distribution of northern Platycheirus-species along the Boreal and Arctic parts of Scandinavia reflects its worldwide Holarctic and Palearctic relations. (Less)