Arable field margins sown with red clover Trifolium pratense and white melilot Melilota alba are particularly attractive to bumblebees, honey bees and non-syrphid flies in Uppland, central Sweden

1 - Field margin sown with a mix of legumes dominated by white melilot Melilota alba;

2 - Field margin sown with a mix of legumes and grasses dominated by red clover Trifolium pratense;

3 - Weedy field margin, allowed to naturally regenerate;

4 - Field margin along a ditch, with naturally occurring herbs and grasses;

5 - Natural species-rich dry pasture.

All flower visiting insects were counted three times a week, both morning and evening, during summer 1989, using a slow transect walk method. Insects were classed as honey bees Apis mellifera, bumblebees Bombus spp., butterflies and moths (Lepidotera), hoverflies (Diptera: Syrphidae) or other insects (mostly Diptera). Some larger insects were identified to species.

Pollen collected by the workers of a honey bee hive placed about 1 km away was examined.

Bumblebees were most abundant on red clover (treatment 2), with 72% of a total of 413 individual bumblebees recorded on that treatment. 98% of the 2,422 honey bees and 69% of the 984 non-Syrphid flies were recorded on melilot plots (treatment 1). Bumblebees were also significantly more common on white melilot than other treatments.

Hoverflies showed no difference between treatments. Butterflies were slightly more species-rich (8 species) on treatment 5 than other treatments (4–6 species)

White melilot, red clover and turnip rape Brassica napus and B. rapa dominated the honey bee pollen loads. Red clover pollen was also being collected elsewhere, because it was still collected after the treatment plots were harvested.

The authors conclude that cultivated leguminous plants are particularly beneficial for bumblebees and honey bees, but a diversity of wild plant species is favourable for other pollinator groups.