Sometimes confused with bumble bee species, the eastern carpenter bee (Xylocopa virginica) is a large, burly bee, renowned for its ability to chew and tunnel into wood, as well as provide a useful pollination service. Here, we'll look at what scientific study tells us about this interesting bee species.
The eastern carpenter bee (Xylocopa virginica) is established throughout eastern North America (from Southern Canada to Florida and Texas, and extending into the mid-west). It has also been found as far west as Colorado4.
Eastern carpenter bees make nests in exactly the same way as other carpenter bees, but will nest either in groups or as a solitary bee5.
It is thought that this behavior is dependent on the availability of nest sites and materials, and climactic conditions – so if nesting resources are readily available, then the eastern carpenter bee queens seem to prefer to nest as solitary bees, whereas, if nesting resources are less abundant, they will nest as groups4.
The behavior of eastern carpenter bees in nests is quite different from honey bees and bumble bees. Honey bee and bumble bee nests have one female that mates and lays eggs (the queen), with all the other worker females caring for the queen, the brood, and the nest.
In social eastern carpenter bee nests, however, all female bees can mate and produce offspring, although it does seem that there is usually just one female (often referred to as the ‘primary female’) that produces young and forages to feed the offspring and the other female bees, while the rest of the females care for and protect the nest4,5.
The death of a ‘primary female’ will lead to supersedure – wherein a ’secondary female’ will take the place of the deceased ‘primary female’5.
Social nests contain 2 – 5 adult female bees, but social nests do not generate more brood than solitary nests5. Males are territorial – especially around the nest - seeking to protect the nest and find mating opportunities.
It has been observed that eastern carpenter bees’ abandoned nests are sometimes occupied by female giant resin bees (Megachile sculpturalis)1,2,3 . The resin bees do this because they can’t excavate holes in wood themselves, so they occupy pre-existing, but abandoned nests.
Eastern carpenter bees have an abdomen that is mostly glossy black, with a slight metallic tint6. The thorax is covered in pale ginger hair.
Females have black faces, whereas males can easily be distinguished from females due to their white faces. It is also known that males have a larger thoracic volume than females7.
It seems to be possible to distinguish the social order of females of eastern carpenter bee based on the amount of wear and tear of the mandibles (jaws) and the wings: primary females tend to have more wear of mandibles and visible wing damage than secondary or tertiary females, because they carry out more foraging and nesting behaviors8.
Additionally, primary females are larger than the other females8.
This excellent piece of short video footage captures three points of interest to look out for:
The bumble bee, Bombus impatiens is similar in appearance to the eastern carpenter bee, but the abdomen is visibly more hairy.
Eastern carpenter bees belong to the Apidae bee family, and are categorized as having long tongues.
For food, the eastern carpenter bee relies on pollen and nectar. They are polylectic11 (they will visit a wide range of flowering plants).
As noted from the above video, they are (like many bee species) adept at nectar robbing – a behavior reported in eastern carpenter bees as long ago as 1875 by Gentry9.
There is some debate as to whether the eastern carpenter bee is a friend or a pest, and which is most prominent: their pollination role (and ability to buzz pollinate) or their destructive effect on man-made wooden structures.
It does seem, however, that their effect on man-made structures is rather limited. According to Williams and Winifree10 (Bryn Mawr College and Rutgers University):
They are also know to pollinate a number of important crops8.
The short video below provides evidence of female eastern carpenter bees pollinating passion flower, Passiflora incarnata. As the video continues, each female becomes increasingly covered in pollen grains, particularly on the head and thorax.
Note how the very hairy rear legs of this species are also well adapted to collect pollen.
It is notable by the 'ragged' appearance of the wings and thorax these females are clearly ‘primary females’.