Landscaping pebbles attract nesting by the native ground-nesting bee Halictus rubicundus (Hymenoptera: Halictidae)

Authors: Cane, James

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2015
Publication Date: 4/15/2015
Publication URL: http://DOI: 10.1007/s13592-015-0364z.
Citation: Cane, J.H. 2015. Landscaping pebbles attract nesting by the native ground-nesting bee Halictus rubicundus (Hymenoptera: Halictidae). Apidologie. 46(6):728-734.

Interpretive Summary: Most species of bees nest in the soil. Pollinator-friendly gardening and landscaping practices focus on providing flowers useful to bees for pollen and nectar to feed their progeny. We know far less about providing for the other need of these bees, namely, nesting habitat. In this experimental study, we tested the attractiveness of a soil surface strewn with small stream pebbles for use by a ground nesting bee. The species studied is a common representative of a ubiquitous genus of ground-nesting bee found in many urban gardens. Females invariably preferred to nest amid the stream pebble surface mulch over simple bare soil. A pebble mulch is aesthetically pleasing, affordable, easily spread, and it deters erosion, and now we know that it complements a flower garden in providing for the nesting needs of some of our native bees.

Technical Abstract: Most species of bees nest underground. Recent interest in pollinator-friendly gardens and landscaping focuses on planting suitable flowering species for bees, but we know little about providing for the ground-nesting needs of bees other than leaving them bare dirt surfaces. In this study, a surface layer of decorative flat stream pebbles was experimentally deployed in 24 paired subplots amid a nesting aggregation of the bee Halictus rubicundus. Over two years, females consistently preferred to nest amid the pebbles rather than adjacent bare dirt. Species of Halictus and their relatives (Lasioglossum, Dialictus, Evylaeus, Agapostemon) are widespread native floral generalists found in many urban areas of the northern hemisphere. Discovery of this practical soil nesting enhancement for H. rubicundus offers an aesthetically acceptable landscaping technique to promote these bees’ nesting, particularly where pollinator gardens and bee-friendly landscaping is already being provided.