Pubescent Carpenter Bee

Appearance

Females are large and shiny, black with yellow markings on their heads. Males are smaller than females, distinguished by a narrow head and yellow pubescence that covers their entire bodies.

Behavior

"X. pubescens" cannot forage in temperatures below 18 degrees Celsius, likely due to the energy needed to maintain body heat for their large size. "X. pubescens" has been found to forage on 30 different plant species in India and 61 different species in Israel. It gathers both nectar and pollen from plants in the spring, summer and fall. In the winter, only nectar is gathered and foraging can only be accomplished on warm days. Mutualism is observed between "X. pubescens" and several species of plants, as the species pollinated by "X. pubescens" have been observed to have low or zero fruit set rate if not pollinated by it. "X. pubescens" is also able to avoid revisiting plants on which it has already foraged by marking the plant with pheromones.Breeding season is early March to early November. Most mating occurs in the spring, but some still occurs in the fall. Mating is not yet well understood in "X. pubescens". Males make territorial flights in shaded areas at a height ranging from a few centimeters to a few meters. These territories have been shown to be desirable by all males, as competition for them is common. In the case of an intruder, a male will charge the intruder to drive him away. If the intruder does not avoid the charging male, the charging male will bash the intruder with his head and will continue this pattern until the intruder is driven off. Females come into these male territories to mate, but the mechanics of how this works are not yet known."X. pubescens" have glands that are vital in their exocrine system and play a large part in communication. One category of glands is the intersegmental glands, also known as the yellow glands. The intersegmental glands are made up of several gland pairs in the abdomen, which open up into the intersegmental membranes. These glands distinguish non-nesting bees from bees that are actively breeding. In non-nesting bees they are compact and white. They increase in size and turn from white to yellow as breeding season progresses. Unicellular secretory elements in these glands empty through a duct into the intersegmental membranes, from which the chemicals are released. The other important glands, especially for communication, is the Dufour's gland. The original role of these glands in various bee species was to produce the brood cell lining, but this function does not exist in "Xylocopa" species. Instead, these glands are responsible for the production of scent marking pheromones. These are strictly hydrocarbons in "X. pubescens", and are used to mark flowers that have been previously visiting on foraging trips in order to avoid them. These scent markings on previously visited flowers are recognized both by "X. pubescens" and "X. sulcatipes", which allows the two species to be more efficient in foraging. This system of scent marking is also involved in nest recognition.

Reproduction

Reproductive suppression is often used in social insect colonies by queens to maintain a genetic monopoly of the offspring in the nest. Some species suppress worker egg laying through pheromones and chemical control. However, in "Xylocopa pubescens", the dominant female of the nest suppresses reproduction of any other females in the nest by preventing them access to the cell in the tunnels of the nest necessary for eggs. The only way that another female in the nest can reproduce is if she takes over the nest by force, or leaves to either take over another nest or found her own.

Predators

Ants of various species have been found to invade nests in some "Xylocopa" species. Specifically, "Monomorium gracillimum" have been observed to invade the nests of "X. pubescens". The ants dig small holes in the tunnel walls of "X. pubescens" to get into the nest. No confrontation occurs, as the mother attempts to remove as many of her brood as she can before the destruction of the nest and all brood cells. Additionally, because nesting takes place in wood, termites have been found to infiltrate nests, eat the walls, and fill it with refuse. Birds have also been observed to feed on "X. pubescens", specifically the woodpecker species "Dendrocopos syriacus" in Mediterranean regions.

Cultural

Carpenter bees have been observed pollinating agricultural plants such as passionflower and cotton, but "X. pubescens" do not naturally pollinate any agricultural plants. However, in a greenhouse setting, "X. pubescens" have been shown to be a more effective pollinator of honeydew melon than honeybees by increasing the fruit set three times more than a honeybee. The obstacle for using "X. pubescens" for agricultural purposes is that ways to mass-rear them have not yet been developed.