Soil textures of nest partitions made by the mason bees Osmia lignaria and O. cornifrons (Hymenoptera: Megachilidae)

Abstract

Osmia lignaria and O. cornifrons require mineral soil to build partitions between cells in their nests. We examined the textures of soil collected by these bees, using laser particle size analysis. For both species, soil in the nest was generally loam or sandy loam in texture, although individual partitions had wide variation in particle size. Partitions in O. cornifrons nests had 5.8% higher clay content than those in O. lignaria nests. Textural trends were similar when data from individual partitions were analyzed. For both species, we found no significant effect of nearby soil texture or the position of the partition in the nest, on the texture of individual partitions. Observations of partitions indicate that some females collect soil material from different locations to build one single partition. These results shed new light on the ecology of soil used by cavity nesting mason bees, with implications for their management as alternative pollinators.