They thought it was extinct: Bee seen for the first time since 1973

University of Copenhagen scientists have found 127 of a total of 296 species of bees in Denmark in the research project, Grazing4diversity. Some of them are very rare.

This applies, for example, to the halictus leucaheneus, which was last seen on the Røsnæs peninsula in 1973, and the rare and critically endangered species of bee Lasioglossum Aeratum that Grazing4diversity has spotted for the first time off the island of Bornholm, namely near Vordingborg and on the Røsnæs peninsula on Zealand.

One of the researchers from Grazing4diversity is bee expert Hjalte Carlberg Ro-Poulsen, a postdoc at the Department of Geosciences and Natural Resource Management.

He explains that the bees were found in two collection events in July 2021 and May 2022, because there is a big difference between the species that can be found in May and in July, and that is why the researchers were in the field on two occasions. The greatest diversity and bee numbers are to be found in July, and this is when the halictus leucaheneus appeared.

Coloured plastic plates

The researchers had 169 sample venues in 42 locations in Denmark. They worked in teams of three to four people in order to be able to collect at all the sample venues at roughly the same time.

Different types of traps were used, and the majority of the bees were caught with so-called pan traps.

A pan trap consists of three plastic plates – one white, one yellow and one blue – filled with liquid. The colours attract the insects, who think it is a flower, and when they land, they fall into the liquid.

The halictus leucaheneus was found in a sweep sample, namely the contents of an insect net that the researchers use to flap at the vegetation for ten minutes.

Grazing cattle and horses

The researchers got the halictus leucaheneus into the trap at a military exercise area near Jægerspris in North Zealand. The discovery is important because the species is not only extremely rare in Denmark, but is also red-listed as a vulnerable species in the rest of Europe.

According to Hjalte Carlberg Ro-Poulsen, it would soon have been declared nationally extinct if it were not for Grazing4diversity.

According to a press release from UCPH, the bee scientists have a strong presumption that the best way to give nature back to the bees is to let cattle and horses graze all year round, because they contribute important processes to the natural ecosystem.

This method requires a minimum of human interference.