Order: Hymenoptera
Family: Andrenidae
Species: Andrena spp.

Description and Life History
This past spring and early summer we have had a number of mining bees submitted to the clinic. This is unusual because Andrenid bees are not commonly encountered in Whatcom County.

Mining bees (or Andrenid bees) resemble the typical honeybee in shape and size. Bodies are colored dark with fine light brown or yellow hairs. Andrenid bees have chewing-lapping mouthparts used to manipulate and collect flower products such as nectar and pollen. The protruding ‘lapping’ mouthpart is shorter in mining bees than honeybees giving them the common name of short-tongued bees.

Unlike honeybees, mining bees are solitary and do not form large, socially organized nests. As their name suggests, mining bees dig single nests in the soil. In spring, adult bees emerge, mate and begin nest preparation. Bees select exposed, well-drained soils to nest in such as banks, hills and road cut-outs. Although the bees are solitary nesters, they often construct nests in large numbers next to one another at a given nesting site. Each female mines out a cylindrical hole to raise offspring. The nest consists of a vertical tunnel and side cells along side the tunnel for hatching eggs. Females forage flowers in spring to buildup food reserve to raise the young. Once a cell has adequate food reserves, the female deposits an egg. The hatching larva feeds on the food reserves throughout the summer. Foraging activity generally lessens during the summer months and the bees become less noticeable. Mature larvae pupate and transform in adults during the late summer. Adults spend the winter inside the burrow and will emerge the following spring to start the whole cycle over.

Damage
When bees nest together in large numbers, they can be quite ominous, especially during mating and foraging seasons. Mining bees can sting, however they are not easily provoked. The bees are often described as docile. Customers submitting samples have complained about stings by these bees.

Management
Mining bees are important pollinators; bees should be tolerated if there is no physical danger posed by the bees. Mining bees are particular about the habitat that they nest in. Areas that are dry, exposed and well-drained with sparse vegetation are the preferred nesting sites. If a problem is encountered by ground-nesting bees such as these, consider mulching the soil with organic matter and fiber (such as paper or cardboard) or re-vegetating the landscape. This will make the place inhabitable for the bees and they will move on to another site next year.

Drier springs maybe a contributing factor to the recent increase in occurrence of mining bees. Mining bees do not inhabit wet soils readily. Regular watering of the ground where bees are nesting may deter them from settling in April and May.

Using insecticides for managing areas of mining bees should only be considered when people’s safety is at risk and as a last option. Insecticide recommendations for ground nesting bees and wasps will manage mining bees. Refer to WSU Extension Bulletin EB 0643 http://cru.cahe.wsu.edu/CEPublications/eb0643/eb0643.pdf for current insecticide recommendations.