Bumblebees and butterflies in Norway

Study Extent

Butterflies and bumblebees are monitored in a total of 52 sites from the Lucas-grid in Norway (country covering grid network with 18 km distance between grids); 17 sites in the region containing former counties Østfold (now part of county Viken) and Vestfold (now part of county Vestfold and Telemark), 18 sites in the county Trøndelag, and 17 sites in the region containing the former county of Vest-Agder (now part of county Agder) and county Rogaland. The sites are selected using a gridded network of 1.5 * 1.5 km squares, placed 18 x 18 km apart. In each square, a total of 1 km transects (20 transects á 50 m) are placed in suitable environments (open forest- and grassland). Butterflies and bumblebees are counted and determined to species. The vegetative cover of flowering plants is also registered during the inventories, as well as weather parameters and the time at the start and end of the recording on the transects. The transects are visited three times during the summer in order to encompass the phenological range of different species, specifically in the spring, mid-summer and late summer.

Sampling

Registration of bumblebees and butterflies are made three times each summer on each transect; in late spring, mid-summer and late summer. The field work is carried out by volunteer personnel instructed to follow a standardized field protocol. The volunteers follow predefined transect lines, which they locate using GPS. To ensure that the counts are standardized as much as possible, transect walks are undertaken between 10.00 and 17.00 and only when weather conditions are suitable for the activity of the monitored insects (above 15 °C, maximum 60 % cloud cover, little wind). During the transect walks, butterflies and bumblebees 2.5 meter to each side and 5 m ahead are registered both in species and number. If necessary, the insects are caught using a sweep net for closer investigation. The total cover of flowering plants (scale from 0-3), weather conditions (temperature and cloudiness), and time is also documented for each transect.

Method steps

1. These data are collected in a project where butterflies and bumblebees are monitored yearly in three regions of Norway.

There are 35 bumblebee species and around 100 butterfly species in Norway. This monitoring project focus on the species that can be found in open grass- and forestland in the regions included in the project, although all species, even the unexpected ones, found on transects are registered. All species of the genus Bombus found are registered (see Norwegian species list of bumblebees on https://artsdatabanken.no/Pages/231205/Oversikt_over_alle_humler_i), and all species of the butterfly families Papilionidae, Hesperiidae, Pieridae, Lycaenidae, Nymhalidae, and Zygaenidae found are registered (see Norwegian species list of butterflies on https://artsdatabanken.no/arter-pa-nett/sommerfugler).

1. Bombus
   common name: bumblebees rank: genus
2. Lepidoptera
   common name: butterflies rank: order

Butterflies and bumblebees are registered in the regions containing former counties Østfold (now part of county Viken) and Vestfold (now part of county Vestfold and Telemark), in the county Trøndelag, and in the region containing the former county of Vest-Agder (now part of county Agder) and county Rogaland.