Species of the Month, May 2014: Eastern Carpenter Bee

This is the fifth post in our "Species of the Month" series, written by Park Ecologist Peter VanLinn. It's one of several 2014 initiatives meant to share knowledge we have about the Park for those who love it. This month, we spotlight the Eastern Carpenter Bee.

While you are out exploring the forest and wildflowers of Forest Park this summer, keep an eye out for May’s Species of the Month, the Eastern carpenter bee. The carpenter bee is one of many native bees that use Missouri and its native wildflowers for habitat. The carpenter bee helps pollinate many native wildflowers and other garden plants while searching from plant to plant for nectar.

However, pesticide use and habitat destruction continue to impact the carpenter bee’s ability to provide pollination for our fruits, vegetables and native wildflowers.  If you would like to help you can try not using neonicotinoid pesticides, or any pesticides if you can help it. You can also establish a place for carpenter bees to nest by drilling some holes into (but not all the way through) a block of wood or a log. Placing this type of nesting habitat in your yard helps keep the bees away from your house in near your garden.

 Bee block photo courtesy of  tcbeekepers.org

Bee block photo courtesy of tcbeekepers.org

Forest Park Locations: Throughout the Park, especially in forested areas containing wildflowers, such as Kennedy Savanna and Kennedy Forest, Deer Lake Savanna and Steinberg Prairie.

Identification: 

  • Description: Though Eastern carpenter bees somewhat resemble bumblebees, they have a distinguishable shiny black abdomen, whereas bumblebees' abdomens are fuzzy and often contain a band of yellow. Behavior can also help distinguish carpenter bees from bumblebees because carpenter bees are mostly solitary and excavate their nests in wood, boring a uniformly circular hole about 3/8 inch in diameter and leaving behind a small pile of sawdust.
  • Total length: About 3/4 to just more than 1 inch.
  • Longevity: Males typically live for 1 year; females can live longer.

Distribution: Statewide throughout Missouri and extending across eastern and east-central U.S and into southern Canada; the only member of its genus in most of its range.

Habitat: Carpenter bees are most often found in forested areas with adjacent wildflower populations used for nectar foraging. Unfinished wood is needed for boring nest holes; wood preferences include softwoods like redwood, cypress, cedar and pine.  

Life Cycle: Adults spend the winter in nests constructed the previous year, and become active in April or May. After mating, females construct new nesting tunnels or use preexisting tunnels. Tunnels are clean cut and may extend 6 to 8 inches. Females collect pollen and nectar to produce a dough-like mass called "bee bread." Eggs hatch into larvae that feed on the bee bread in their cells. Development varies but can progress from egg to adult in a little over a month. There may be two or three generations per year. Continuous generations may occur. Adults emerging in late summer or fall do not mate until spring but may gather and store pollen in their tunnels.

Behavior: As with many members of the ants, bees and wasps group, the females of this species are capable of stinging when molested, while the males lack stingers altogether. The males often startle people with their aggressive-looking territorial hovering, but although they investigate anything new in their territories, they are interested only in combating rival males. They are uninterested in people. The white-faced males are often seen at this time hovering in a pendulous, bobbing dance near nests, waiting for females. These males rush to investigate any airborne object—a thrown pebble for example—that comes near them.

Food: Adults feed on nectar from flowers, sometimes biting a hole in the base of the petals to "rob" the nectar without pollinating. They do pollinate many flowers, however, including "maypop" or passionflower. The female provisions her nest tunnels with nectar and pollen and then lays eggs on this food, which nourishes the young as they develop.

 Photo courtesy of Johnny N. Dell,  Bugwood.org

Photo courtesy of Johnny N. Dell, Bugwood.org

Human Connections: Structural damage to timber can result when there are many nests and when woodpeckers enlarge the holes to feed on the larval or overwintering bees. Because carpenter bees are important pollinators, some farmers encourage their presence by providing blocks of wood attractive to them and by not using pesticides that harm, such as neonicotinoids. Humans can also promote pollination and carpenter bee production by constructing bee blocks (artificial bee houses) by drilling various sized holes into blocks of wood and posting them near flowers. These bee blocks will help improve your garden and keep bees away from wood structures on your house.

Ecosystem Connections: Carpenter bees are important pollinators for many types of plants. In nature, their tunneling into soft, dry, rotting wood speeds decomposition, helping to recycle nutrients back into the soil. Biologists study carpenter bees because their behavior seems transitional between solitary and true social behavior.

Interesting Fact: Carpenter bees have an interesting evolutionary survival tactic. The offspring of carpenter bees are sexually biased, meaning there is a bias toward producing more females. Females are generally found to be 60% of the offspring production. Carpenter bees also have a bias toward females in the order in which eggs are laid; 98% of first eggs laid are female. Another way carpenter bees take advantage of this is by laying female eggs first and deeper into nest tunnels, sacrificing the male eggs to any predators that might invade.

Note: Information has been collected from the the Missouri Department of Conservation: Online Field Guide, the Texas A&M: AgriLife Extension Online Field Guide and Sex Allocation by Stuart West, in “Monographs in Population Biology."