Eastern carpenter bee

Female X. virginica can have solitary nests, but they usually nest in social groups. The social order of X. virginica is broken into three groups: primary, secondary, and tertiary. Primary females act as the dominant within a nest and are in charge of reproduction, providing food for the larvae, and laying all the eggs. This is different from many bee species in which there is a queen that focuses her energy solely on laying eggs while relying on provisions provide by subordinate bees. Secondary females may sometimes participate in oviposition, and they reinforce this potential role by helping provide for the larvae or performing nest maintenance. Tertiary females rely on the provisions provided by primary females and quietly await overwintering while remaining inactive.[3]

Studies have shown that primary females are usually the bees that have overwintered twice, while tertiary bees have only overwintered once. Tertiary bees will most likely survive a second overwintering and develop further to become primary female the following year. Secondary bees may survive a second winter, but that is unlikely if they actively forage after their first overwintering.[3]

Not all females do the same work in a social nest. This is evident based on the varying levels of wear on the wings and mandibles of females of various social standing. Although many nests have more than one female, there is a division of labor between the older and younger females. During nesting time, only the older females are responsible for nesting duties such as digging, excavating the cells, lining the cells, collecting food, and ovipositing. Evidence of this activity can be found in their worn mandibles. Young females rarely leave the nest and guard the entrance while the older females work, resulting in unworn wings and mandibles in the younger females.[2] Additionally, X. virginica is the only known species in which one-year-old females cohabit the nest with two-year-old females that do all the labor.[10]

Males often spend long periods of time hovering, flying, or in fast pursuit of intruders, while female flight activity is usually very directed, such as flights to flowers and food sites. Larger females have an advantage because they can carry larger amounts of pollen or nectar back to the nest and can fly longer distances.[5]

Carpenter bee on milkweed (Asclepias) flower, carrying pollinia.

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.[2] 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.[11]

Males will establish territories near an active nest entrance to protect the colony and seek mating opportunities. For males that are near the nest entrance, their boundaries are usually linear and several meters long. For males that are farther from the exit, their boundaries are usually in the shape of a square and shorter in length. Males can stay in one territory for as long as two weeks. Although they do most of their foraging and resting during the night, they take small breaks throughout the day as well. After these breaks, they often have to fight off intruders that have taken advantage of their absence.[2]

Flights near the nest are usually uniform and involve much hovering.[2] Flights protecting a bee's territory can be as short as a few minutes, but may extend beyond an hour. Males will not react to another bee unless the other is flying at high speed. When other individuals hover near the nest, it is unlikely that the male will pursue, whereas if another male comes into a territory at a high speed, the territorial male will give chase. When males patrolling the entrance of a nest are confronted with either dead or living Eastern carpenter bees suspended from a thread and dangled within the male's territory, the male does not respond when the bee is suspended and motionless, whether it is living or dead—even though X. virginica are capable of recognizing other individuals of their species. However, when the suspended bee is released and allowed to fly in the male's territory or is swung through the territory on the thread, the territorial male pursues it.[2]

There is one common species of bombyliid flies known to parasitize the larvae of Xylocopa virginica: Xenox tigrinus.

Eastern carpenter bees have mandibular glands that are known to produce a marking chemical in X. hirsutissima that functions as a nest marker or for female attraction. The glands are present in both males and females, but they produce no marking substance.[2] However, X. virginica does have a Dufour's gland that is used to deposit a scent on a flower immediately following nectar collection. The scent, composed of hydrocarbons and esters, discourages X. virginica, as well as other bee species, from returning to that same flower.[10]

The male bee is unable to sting because the stinger is simply a modified ovipositor (which males lack by definition), though they will commonly approach human beings and buzz loudly around them or fly close to them. The female, on the other hand, is capable of stinging; while the pain level of these stings is not well-documented, researchers have testified that X. virginica will sting if roughly handled.[6][13] As the stinger is not barbed, a female can sting multiple times.

X. virginica visits many different kinds of flowers in order to gather pollen and nectar to bring back to the nest for larvae. Most of the plants they visit are wild grown or grown for decorative value;[6] however, they can be good pollinators of blueberry crops.[14] Their active seasons are quite long, and they forage on a wide variety of plant species. Also, because the start of their activity season is dependent on temperature, it is easy for greenhouse workers to manipulate the beginning of foraging activity.[11] However, in comparison to species such as the honey bee, their smaller nest makes them less powerful as pollinators.[15]

Because X. virginica builds its nests in various types of wood, it presents the disadvantage of weakening wood in manmade structures. They are also able to produce an excrement upon exiting their tunnels that may splash on the sides of buildings and negatively affect the aesthetic appeal of that structure. However, when weighed against the benefits X. virginica have as pollinators, the costs of its destructive behavior are insignificant. X. virginica offer benefits in the form of pollination for fruits, vegetables, legumes, and flower crops. Although the pollination strengths of X. virginica are secondary to that of the bumblebees and honey bees, the contribution is great enough to overlook destructive tendencies.[6] X. virginica avoid entrances that are stained white, which is a possible solution to keeping them out of unwanted areas.[10]