In the last few weeks of March last year I watched some very busy bees visiting flowers of the native highbush blueberry bush planted just outside my home office window. They also visited the hybrid rabbiteye blueberry bushes in our yard and at the nursery. They look and sound like bumble bees, except they are smaller and faster. These are Southeastern blueberry bees, native to the southeastern U. S., and they forage primarily on blueberries. What amazes me is that they are active only for a short period of time each year, which coincides with blueberry flowering of mid March into April in our area. Blueberry flowers are visited by honey bees, bumble bees, carpenter bees and the southeastern blueberry bee. Carpenter bees are nectar robbers. They are able to make a small slit at the base of the flower to rob nectar without brushing against the pollen structures. For this reason, they are not good pollinators of blueberries. The non-native honey bee commonly uses the holes made by carpenter bees.
Blueberry flowers contain a male part called an anther that is tubular in shape with an opening at one end from which the pollen is dispersed. The blueberry bee attaches to the flower and vibrates her flight muscles very rapidly which causes the anther to work like a salt shaker, shaking pollen out of the opening. This is called buzz pollination. When the bee goes to the next flower, her vibrating flight muscles shake out pollen again and also causes the pollen clinging to her body to attach to the stigma, the female part of the flower. Thus pollination occurs, resulting in the eventual delicious blueberry fruit surrounding the seeds.
Honey bees are not able to buzz pollinate. Bumble bees can pollinate blueberry flowers successfully through buzz pollination but their numbers are comparatively low in early spring. They are, however, the major pollinators of tomato plants which also need buzz pollination.
So where and how do these blueberry bees live? They are solitary ground nesting bees. They dig burrows in sandy or loose soil. Sometimes they burrow beneath hardwood forest leaf litter or in the walls of earthen holes, perhaps where a tree was uprooted exposing a hole and soft soil.
Ground nesting bees choose a bare, sunny spot that is not likely to flood. They dig a long tunnel slightly wider than their own bodies. They may do this by themselves or they may do it in the company of other bees of their own species. They are still solitary in that each bee digs her own nest and provisions her own brood. At the end of the tunnel, she builds a brood cell chamber for one baby, a larva. The mother bee fills the brood cell with enough pollen and nectar for one bee to grow from egg to adult. She lays an egg and seals the chamber .Then she may add branches to the tunnel where she provisions another cell at the end of each branch. Blueberry bees produce one generation per year and adults are active for only 3-5 weeks.
Solitary bees do not have colonies to defend, so would only sting if you accidentally crushed them. Don't be afraid to get up close to watch these blueberry bees moving quickly from flower to flower, gathering pollen.
There are three things you can do to encourage Southeastern blueberry bees. First plant their favorite plant, blueberry bushes! Second, avoid using pesticides. Blueberries are generally pest free and very easy to grow, but you also should not use lawn pesticides which could affect underground nesting bees. Finally, allow natural patches of exposed soil as part of the habitat in your yard; this could be an area of patchy lawn or mowed weeds. Loosen up a little and have a slightly wilder yard.
For more information about Southeastern blueberry bees and other native bees such as bumble bees and sweat bees, contact The Xerces Society for Invertebrate Conservation at www.xerces.org.
