Bombus impatiens, the common eastern bumble bee, is the most commonly encountered bumblebee across much of eastern North America. They can be found in the Eastern temperate forest region of the eastern United States, southern Canada, and the eastern Great Plains. Because of their great adaptability, they can live in country, suburbs, and even urban cities. This adaptability makes them a great pollinator species, leading to an increase in their commercial use by the greenhouse industry. This increase consequently led to their farther spread outside their previous distribution range. They are considered one of the most important species of pollinator bees in North America.
Taxonomy and phylogeny
The generic epithet (the first part of the name) Bombus comes from the genus Bombus, which is also commonly known as bumblebee and belongs to the tribe Bombini. The specific name (the latter half of its scientific name) may come from the flowers of the genus Impatiens, which is one of its food sources.
Including B. impatiens, the genus Bombus contains 250 species and most species are characterized by their eusociality or parasitic nature. Specifically, the genus Bombus has 49 subgenera, and B. impatiens belongs to the subgenus Pyrobombus. B. impatiens is also of the order Hymenoptera and family Apidae which characterizes its kin selection and relatedness.
Description and Identification
Queens, workers, and males
The bees of B. impatiens are similar to those of B. bimaculatus, B. perplexus, B. vagans, B. sandersoni, and B. separatus in their appearance. They have short and even hair, medium-sized heads with cheeks that are similar in width to their heads, and a long and rectangular body. In general, queens and workers are similar in their coloring, pubescence, and structure. However, with a body length of 17–23 mm, queens have bigger bodies than males or workers. Workers have bodies that are 8.5–16 mm, and males have bodies that are 12–18 mm long. The differences in their sizes can be observed by the differences in their larval weight at second instar. In addition to the difference in their sizes, males slightly differ in their coloring. While queens and workers are both black with a yellow thorax and first abdominal segment, males have a yellow face and head.
Nests
B. impatiens have underground nests that are 1–3 feet below the ground surface. They enter their nests using tunnels that are 18 inches to 9 feet long. Unlike the nests of honeybees or paper wasps, the nests of B. impatiens do not have a predictable pattern. The bees lay egg clumps all over inside the nest instead of having one brood area around which the workers’ distribution center is arranged.
Within the nest there is a special division of labor and social organization. 11–13% of workers maintain small spatial fidelity zones inside the nest, and all workers remain at a specific distance from the colony center. Smaller individuals maintained smaller spatial zones and tended to be closer to the center of the nest. Individuals that perform the in-nest task of larval feeding were found in the center of the nest, while foragers were often found on the periphery of the nest when not foraging.
Distribution and habitat
Broadly, they can be found in the Eastern temperate forest region of the eastern United States, southern Canada, and the eastern Great Plains. More specifically, its range includes Ontario, the New England States, Georgia, Mississippi, Kentucky, Tennessee, Alabama, Maryland, Delaware, New Jersey, New York, Pennsylvania, South Carolina, North Carolina, Virginia, West Virginia, south to Florida, west to Michigan, Illinois, Minnesota, Kansas, Missouri, and Iowa. Also, the increase in their commercial use by greenhouse industry led to the spread of the species outside its previous distribution range. Bombus impatiens adapts well to a variety of habitats, nectar sources, and climates and was seen visiting a variety and abundance of plants. In addition to agricultural, wetland, and urban conditions, the species can thrive in wooded habitats, and is likely related to woodland spring ephemerals. It nests underground in open fields and woods.
Colony
To start colonies, the gynes usually leave their hibernacula starting in mid-April and establish colonies in May. In the beginning of June, the workers start to emerge and in August and September the male bees and young queens start appearing. However, at times, the bees can emerge around late to mid-October. In terms of colony sizes, a colony of B. impatiens consists of more than 450 individual bees and most are worker bees.