Xylocopa virginica, sometimes referred to as the eastern carpenter bee, extends through the eastern United States and into Canada. They are sympatric with Xylocopa micans in much of southeastern United States. They nest in various types of wood and eat pollen and nectar. In X. virginica, dominant females do not focus solely on egg-laying, as in other bee species considered to have "queens". Instead, dominant X. virginica females are responsible for a full gamut of activities including reproduction, foraging, and nest construction, whereas subordinate bees may engage in little activity outside of guarding the nest.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withThe bee is similar in size to bumblebees, but has a glossy, mostly black body with a slight metallic purple tint. X. virginica males and females have generally the same mass, but can be differentiated visually by the male's longer body and the female's wider head. The males also have a white spot on their face. Additionally, the males have larger thoracic volumes for given masses. Females of different social standing can also be told apart based on morphology. Primary females are larger than secondary or tertiary females, and also have more mandibular and wing wear.
X. virginica have distinctive maxillae that are adapted to performing perforations on corolla tubes to reach nectaries. Their maxillae are sharp and wedge-shaped, allowing them to split the side of corolla tubes externally to access the nectar. Eastern carpenter bees also have galae on their maxillae that are shaped like large, flat blades. Bees with sharp galae can use these to further aid in penetrating the corolla tubes.
X. virginica is found throughout much of North America east of the Rocky Mountains and at least as far north as Nebraska, southern Ontario, and Maine.
X. virginica is not a solitary bee species, but it is not truly social either. The weak form of sociality they exhibit, with one female doing the majority of the work and caring for her sisters, may be a transitional step in the evolution of sociality.
X. virginica survive mostly on nectar and pollen. Newly emerged bees do not have food stored in their nest, but they are occasionally brought nectar. X. virginica use their maxillae to penetrate the corolla of plants and reach the nectar stores, a behavior known as nectar robbing. This happens when the bee pierces the corollas of long-tubed flowers, thus accessing nectar without making contact with the anthers and bypassing pollination. In some plants this reduces fruit production and seed number. In other plants, defensive mechanisms allow pollination to occur despite perforation of the corolla.
X. virginica build their nests in wood, bamboo culms, agave stalks, and other comparable materials, but they prefer to nest in milled pine or cedar lumber. The nests are built by scraping wood shavings off of the wall. These shavings are then used to create partitions between nesting cells. The entrance cuts into the wood perpendicular to the grain, but they are built parallel beyond the entrance. These nests may be either social, containing groups of two to five females, or solitary. Social nests are more common, despite the fact that brood productivity is actually lower when females choose to nest together. Because X. virginica builds its nests in wood structures, it is common for it to nest in constructed furniture or buildings. X. virginica is the most common large carpenter bee in eastern North America, and it nests in small groups, so nests are fairly commonly encountered.
The nests are usually round and typically have one to four tunnels. They have multiple branches, with each adult female living and laying eggs in a separate branch but females sharing one common entrance. Because the nests are costly to build, it is common for females to reuse old nests.
In X. virginica, mating occurs only once a year, in the spring. Eggs are laid in July, starting farthest from the exit hole, and by about August and mid-September, larval development has completed and all the pupae have become adults. Researchers suggest that there is a mechanism that synchronizes the emergence time of young that are laid at different times by causing the younger eggs to develop faster. This mechanism prevents bees that would emerge sooner from removing their siblings and decreasing their potential competition.
Bees that have newly emerged have a soft cuticle and white wings. The wings later transition to brown, then to a bluish black. They can fly 3–4 days after emergence, but they remain in their nest for at least two weeks, consuming nectar but not pollen. The juveniles begin the next mating cycle the following spring, so one generation develops in a year.
Females begin to exhibit signs of senescence around July. The indicative behavior includes resting in flowers, remaining in the nest, or even just falling to the ground from flight. Older individuals also crawl, avoid taking flight, and do not struggle when handled by humans. The old bees die by early August, the same time that juveniles emerge from brood cells. Due to the simultaneous nature of expiration of old bees and emergence of new ones, there is little overlap between generations, except for some females that survive a second winter.
Each nest usually has one mated individual. Mating occurs in April and is often accompanied by a bobbing dance that involves about a dozen males and only a few females.
Males require female activity, specifically flight, in mating. Occasionally before mating, the couple will face each other and hover for a few minutes. When the male contacts the female, he mounts her back and attempts to push his abdomen under hers. Copulation then occurs, and it is almost always followed by more mating attempts. If, during copulation, the female lands, the couple will disengage and the male will hover waiting for the female to take flight again; however, although the males almost always disengage and pause copulation when the female lands, there have been instances recorded in which the males will hold on to the female with all six legs and flap his wings in an attempt to lift her back into the air.
Larger males are usually more successful in mating. Because of their competitive advantage due to their size, males will likely claim a territory near female nest sites. Smaller males will stay at foraging sites or other areas they think females may pass so they can mate with reduced competition.
