Increasing bumble bee densities in red clover seed production areas

Spring introduction of 115, 85, and 114 queens of Bombus ruderatus and B. subterraneus in three successive years resulted in a threefold increase in peak population densities (from 2000 to 6000 bees/ha) at a red clever seed production site in the Mackenzie Country in the South Island of New Zealand. There was no carry‐over effect from year to year, and in the season after queen introduction ceased, density dropped to 3000 bees/ha.