Bombus atratus

Bombus atratus is a neotropical bumblebee that is found throughout regions of South America, including Colombia, Ecuador, Brazil, and Argentina. It lives in social colonies that include a founder queen/queens, workers and brood. B. atratus is somewhat unusual because of its potential to oscillate between polygynous (multiple queens) and monogynous (one queen) nesting cycles. Bombus atratus was the first species in the genus Bombus that was discovered to display such polygynous nesting patterns. The polygynous nesting cycles lead to certain specific types of behavior including queen-queen aggression. Nests can also be perennial, which is a characteristic rarely found in other bumblebees.B. atratus can be helpful agriculturally because of their ability to pollinate different species of plants. B. atratus has been found to occupy a range of geographic areas and climates throughout South America. Colonies have the ability to thermoregulate nests and keep them a little bit warmer than the outside environment. Foraging workers use muscle contractions to maintain stable temperatures and coupe with seasonal and daily fluctuations in temperature. B. atratus is a species of the Bombus genus. It is a member of the order Hymenoptera, which includes ants, bees, and wasps. Its family Apidae consists of honey bees, stingless bees, carpenter bees, bumblebees, orchid bees, and cuckoo bees. The tribe Bombini includes bristly bees that feed on nectar or pollen, and the genus Bombus is specific to bumblebees. Within Bombus, B. atrarus is part of the New World subgenus Fervidobombus, which includes closely relates species such as Bombus armeniacus, Bombus muscorum, and Bombus transversalis. B. atratus are predominantly black in color. The throat of the bee is completely black while the abdomen is black with a small amount of lightening/discoloration towards the end. Small, dense fir bristles cover almost the entire body of B. atratus. Like most bumblebees, the abdomen of the bee has a rounded tip and a distinct forewing and hindwing. B.atratus workers have a long tongue that facilitates the process of retrieving nectar from within deep and tubular morphologies of flowers. The antenna of B. atratus are also relatively long. Workers have a wing length that ranges between 4 and 10 mm. Queens are usually two to three times the mass of workers. B. atratus nests are usually found above the ground. Nests have been found in an array of different locations, including warm, tropical areas and cold, high altitude environments. Such a diverse geographic distribution illustrates how B. atratus has the unique ability to adapt to a wide range of conditions and pollen sources. Although most nests are built on the ground, nests have been found elevated in trees above the ground. Research indicates that climate dictates whether a particular B.atratus nest will oscillate between polygynous and monogynous cycles. B.atratus are found throughout South America, including Columbia, Ecuador, Brazil, and Argentina and Brazil. The reference map provides a depiction of B.atratus distribution throughout South America. Nests of B. atratus are circular in shape and have been observed to have a diameter of around 10–30 cm and a height of between 10–20 cm. For those nests found on the ground, the brood comb is usually located in slight cavities a couple of centimeters below ground level. The number of nest entrances varies and seems to be unrelated to any specific property of the colony, such as size. Although most nests usually have multiple entrances, one or two are more active than the others. All nest entrances are subject to intentional modifications by the workers that use the entrance. B. atratus also have the tendency of forming pollen feeding pockets that are attached to larval clusters to facilitate the larval feeding process. The Colony Life Cycle begins when a solitary gyne (a foundress) constructs an egg cell in a slightly underground cavity. This egg cell/brood leads to the first set of house workers and foragers that will help further colony propagation. In order to reproduce, the colony must reach the point where it can birth new drones and gynes. The progression to such a drone and gyne reproductive point is not completely understood. The cycle technically completes when the queen dies and/or the reproductive gynes leave the nest. Polygynous phases can begin (and often do begin) if the queen is replaced by more than one new reproductive queen. Monogynous phases are initiated by conflicting queen-queen interactions that kill all but one rival reproductive queens. Research indicates that B. atratus has the ability to form new colonies at any point in the year regardless of the season. It takes 6 days for eggs to initially develop, 12–13 days for them to go through the larval stage, 8-12 more days after that to proceed through the pupa stage, and another final 24–34 days to fully mature. Egg development also may be slightly delayed in colonies that exist in low temperature, high altitude environments. The colony cycle of B. atratus varies depending upon the particular climate and area that a population is found in. If the queen disappears or gets removed from the colony, she can be replaced by a false queen. This false queen produces both female and male offspring in order to maintain the colony’s development and propagation until the following reproductive phase, which is when new queens are produced. The false queen is usually a mated worker. It has been shown that new colonies can be formed from groups of workers that lack a queen. In such cases, a false queen assumes the role of the queen (as described above) and allows for colony propagation and development until the reproductive phase when new queens are produced. Polygyny is extremely rare in the family Apidea, and B. atratus was the first recorded example of polygyny in bumblebees. Colonies found in high altitude and temperate regions typically conform to an annual cycle with one queen per colony. Colonies found in sub tropical or tropical lowland regions seem to be perennial and oscillate between periods of polygyny and monogyny. Alternations occur between monogynous and polygynous life cycle phases occur two-three times a year, with the durations of each phase lasting from several weeks to months. During period of polygyny, the nest may have up to several queens simultaneously, while periods of monogyny are marked by single queens. Polygyny gives rise to a set of aggressive queen-queen interactions (refer to section below) and dominance hierarchies (refer to section below).