Like bumble bees, wild carpenter bees practice buzz pollination -- that is, they vibrate flight muscles in order to shake pollen from flowers. This makes them key pollinators of tomatoes, eggplants and peppers, which require buzz pollination.  The bees' considerable size and attendant ability to carry prodigious pollen loads make them highly effective crop pollinators.

 

Eastern carpenter bees are also excellent generalist pollinators. During the summer, eastern carpenter bees can be spied most often visiting the blossoms of wild blackberries growing in the park and foraging amid tobacco plants and red bee balm at Stone Barns. The bees are important pollinators of a variety of other native flowers as well, including thistles, mountain mint, goldenrod and coneflowers, all of which they frequent at both locations.

 

You may have noticed these bees hovering near rotting wooden structures.  Male eastern carpenter bees have a characteristic way of flying:  they sometimes circle quickly and then hang suspended in front of you, buzzing loudly in mid-air.  Don't be alarmed: male carpenter bees may fly aggressively, but do not have stingers and do not sting or bite.  Females have stingers but are nonaggressive.

 

Wild bees have various methods of constructing nests -- many native bees nest within holes in the ground.  Carpenter bees are tunnel nesters -- this means that they build tubular nests within wood or plant material. The bees scrape wood fibers from the walls of their tunnels to form a kind of particle board used to divide their nests into separate egg chambers. The bees nonetheless do not eat wood; they feed exclusively on pollen and nectar.

 

The social structure of eastern carpenter bee groups is somewhat unusual.  The bees’ colonies lack a queen.  Instead, groups of dominant older females construct nests, gather pollen and produce eggs.  Younger females guard nest entrances.  Males hover nearby the nests, protecting them from intruders.

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Identification Information:   As shown in the photos at right, the eastern carpenter bee has a bulky black body and a golden-yellow thorax with a black spot in the middle. The female eastern carpenter bee's abdomen looks like patent leather - it is black and shiny.  Female bees of the subspecies found at Stone Barns Center for Food and Agriculture  (Xylocopa virginica virginica) have black eyes and sculpted black helmet-like heads that appear flat in front. Male carpenter bees of the same subspecies look significantly different from the females:  their  bodies are heftier; they usually have white or yellow markings on their faces; their eyes are greenish and protuberant; and their heads lack the sculpted helmet-like shape characteristic of the female bees.

 

The eastern carpenter bee is sometimes confused with bumble bees.  The latter, however, can be distinguished because their abdomens are furry-looking, rather than smooth and shiny like those of carpenter bees.  Eastern carpenter bees also bear a superficial resemblance to the giant resin bee (shown in the photo strip below right),  an invasive species that likes to nest in abandoned carpenter bee nests.  Information on that bee is provided in the Resin Bee page at the end of this guide.

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Eastern Carpenter Bees and "Nectar-Robbing": 

In most bee species, females rather than males gather pollen, thus enabling flower pollination. Male bees do not collect pollen:  instead, they survive by drinking nectar from blossoms.  Females also may drink nectar (in addition to gathering pollen).  

 

Eastern carpenter bees, in their quest for nectar, sometimes engage in a form of foraging known as "nectar robbing".  What exactly is nectar-robbing?  According to Wilson & Carril's The Bees in Your Backyard, carpenter bees' large size prevents them from entering tubular flowers to drink their nectar. When encountering deep, narrow-throated flowers such as blueberry blossoms, the bees use their bladed mouth-parts to slice holes in the bases of the blossoms.  The bees then lap up the nectar without touching the pollen-carrying parts of the flower. Other pollinators thereafter may shun the depleted flowers, arousing fears that such carpenter bee visits curtail pollination. 

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Recent studies of blueberry pollination, however, have suggested that carpenter bee  nectar-robbing is not necessarily detrimental and may at times play a part in enhancing pollination.  A 2004 study of blueberry pollination conducted by entomologists Sampson, Danka and Stringer found that honey bees visited blueberry blossoms by taking advantage of entrances slit open by male eastern carpenter bees.  The carpenter bees' presence thus increased honey bee pollen-gathering on blueberry flowers (as well as secondary honey bee nectar-thieving). The study concluded that nectar-robbing male eastern carpenter bees were benign or even potentially beneficial floral visitors of blueberries.
 

Other studies have shown that nectar-robbing may have a more far-reaching beneficial effect on pollinator habitats. Recent research has revealed that pollinating bees sometimes curtail the time they spend on blossoms depleted by nectar- robbing.  Instead, the bees make several short visits to many flowers (rather than lingering on a few flowers that are well-endowed with nectar).  As a consequence, pollen picked up by the bees is disseminated over a broader group of flowers within a given plant species.  This increases the genetic pool that contributes to seed formation, resulting in a richer, more genetically diverse plant population, which better ensures species survival.

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Eastern Carpenter Bees and Wood Damage:  Eastern carpenter bee colonies are relatively small, and because the bees prefer reusing old nests to constructing new ones, the damage the bees do to houses is circumscribed and easily halted.  Painting nest entrances white deters bees from forming or returning to nesting areas. Painting wood with oil-based paint or polyurethane also effectively prevents carpenter bees from nesting.  Providing alternate nesting sites such as wood blocks drilled with large holes also lures bees away from establishing nesting areas in buildings.  Despite the limited harm carpenter bees sometimes inflict on man-made wooden structures, they merit protection because their benefit to commercial crops and the environment far outweighs their potential for destruction.

 

Related species:    There are two species of large carpenter bees in the eastern United States. The second variety, known as the southern carpenter bee (Xylocopa micans), does not extend as far north as New York.   Southern carpenter bees are solitary and do not cause destruction to manmade wooden structures; instead these bees nest in woody plant material.

 

The southern carpenter bee differs in appearance from the eastern carpenter bee. The female southern carpenter bee, shown at right, lacks the helmet-like head of the eastern carpenter bee; has an iridescent greenish-blue body; and has pale hairs on the first segments of its sternum (underside) and on the tip of its abdomen.  The male southern carpenter bee has a collar of of golden reddish hair on its thorax as well as protuberant green eyes. 

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TAXONOMY  -  Eastern Carpenter Bee

Order:  Hymenoptera 

Family:   Apidae

Subfamily:  Xylocopinae

Genus: Xylocopa                              

Species:  Xylocopa virginica