Native and Solitary Bees in Virginia

Introduction

Although honey bees are well known for their beneficial pollination and honey production, native bees found in Virginia impact humans in various ways, ranging from beneficial to annoying. Even when their presence is undesirable, native bees are important pollinators for fruits, vegetables, and native ecosystems.

Carpenter Bees

Carpenter bees, Xylocopa spp. (Hymenoptera: Apidae), are large, heavy-bodied bees often mistaken for bumble bees (Fig. 1). Their bodies are covered with bright yellow or orange hair, except for the shiny, black abdomens. Adult carpenter bees measure about 2.5 cm (1 inch) long.

Carpenter bees build their nests in wood siding, the ends of logs used in log frame houses, or other areas where bare wood is exposed. Males and females cut a 1.3 cm (0.5 inch) circular hole into the wood with their strong jaws, then tunnel parallel to the surface of the wood. The female stores food and lays eggs in individual cells within the tunnel, where the larvae develop.

Carpenter bees can cause extensive damage to wooden structures. Woodpeckers will also peck out the immature bees, causing further damage. When control is necessary, spray an aerosol insecticide into the entrance hole and plug the opening with wood putty. Traps for carpenter bees are also available. For prevention, remove, treat, or paint exposed wood on structures.

Bumble Bees

Bumble bees, Bombus spp. (Hymenoptera: Apidae), are large, hairy bees with stout bodies (Fig. 2). Unlike carpenter bees, their abdomen is fully covered with hairs. They measure about 2-3 cm (0.5-1.5 inches) long and are usually black and yellow. Their somewhat clumsy nature and the buzzing sound in flight are the source of their common name. Currently, 14 species of bumble bees are found in Virginia.

Bumble bees are often seen foraging on flowers and are cavity nesters. Some species choose nesting places around houses, or wooden storage sheds and small barns. Bumble bees will sometimes use old nests made by small rodents.

Virginia is within the native range for the rusty patched bumble bee (Bombus affinis), which was listed as federally endangered in 2017. If you believe you may have a population of rusty patched bumble bee on your property, contact your local Virginia Cooperative Extension agent (https://ext.vt.edu/offices.html)

Bumble bees are often seen foraging on flowers. Some species choose nesting places around houses, or wooden storage sheds and small barns. Bumble bees will sometimes use old nests made by small rodents.

Bumble bees are beneficial insects, performing pollinating services for crops such as tomato, red clover, and blueberries. Many species collect and carry pollen on their hind legs to bring it back to their nest. Because of their beneficial nature, control is not usually recommended for bumble bees. If necessary, find and destroy the nest. Individual bumble bees that stray indoors can be controlled with an aerosol insecticide.

Andrenid Bees 

Also known as mining bees, andrenid bees (Hymenoptera: Andrenidae) are among the first bees seen in the spring (Fig. 3). Andrenid bees are solitary, ground-nesting bees, but will sometimes nest together in large numbers if they find a suitable patch of soil. They swarm defensively over the ground when people approach their nesting site, but this is more of a bluff because they rarely sting. Andrenid bees are active for only a few weeks each year, when the females excavate tunnels and provision underground cells for their offspring. The immature bees spend the rest of the year underground and emerge as adults next spring.

These are small to moderate-sized bees that look like dark honey bees. They are considered beneficial pollinators of crops and fruit trees and should be left alone if possible. Since they do not like to nest in wet soil, watering their nesting sites during the short nesting time will discourage them from nesting in that spot.

Leafcutter Bees

Leafcutter bees, Hymenoptera: Megachilidae, resemble small dark honey bees with large mandibles. They are solitary bees that cut small holes out of leaves (Fig. 4) to line nesting cells for the immature bees (Fig. 5). They often make nests in doors and window frames and can be a nuisance. The nest can be removed if objectionable, but otherwise they are beneficial pollinators and can be left alone.

Sweat Bees

Sweat bees, Hymenoptera: Halictidae, are noted for their bright, metallic coloration (Fig. 7) and their habit of collecting sweat for the salt. They can sting, especially when caught between clothes and sweaty skin, but they are otherwise non-aggressive and are beneficial pollinators.

Orchard Mason Bees

Orchard mason bees, Osmia spp. (Hymenoptera: Megachilidae) are excellent pollinators for home gardens and orchards (Fig. 8). An individual orchard mason bee can visit up to 60,000 flowers in her lifetime. They are also very docile and rarely sting, making them suitable for urban situations. These bees will build their nests in cracks of wood, tunnels made by other insects, or similar places as long as the opening is just barely wider than their body. They are solitary and do not share tunnels, but they will nest near others of the same species.

Naturally low densities of orchard mason bees can be encouraged with bee houses placed around the property (Fig. 9). Bee houses can be purchased, but making one is easy. Use a block of untreated wood measuring 30 x 10 x 15 cm (12 x 4 x 6 inches). On the 10 cm side, drill holes that are 14 cm (5.5 inches) deep with a 5/16 drill bit. Mason bees will only use holes made with a 5/16 drill bit. Drill the holes about 2 cm (0.75 inch) apart in rows.

To protect the larvae from woodpeckers, place 1.3 cm (0.5 inch) hardware cloth on one side of the block and curve it around to the other side so that it bows out in front of the entrances. Attach firmly on both sides of the block. To reduce the risk of disease and parasites, paper liners can be used to line the holes and replaced each season. Holes capped with mud indicate that orchard mason bees are using the bee house.